Nucleic acid-binding photoprobes and uses thereof

ABSTRACT

The present invention relates to photoactivatable compounds and methods of use thereof for determining binding site and other structural information about RNA transcripts. The invention also provides methods of identifying RNA transcripts that bind compounds and are thus druggable, methods of screening drug candidates, and methods of determining drug binding sites and/or accessible or reactive sites on a target RNA.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. § 119(e) of U.S.Provisional Patent Application Ser. No. 62/593,175, filed Nov. 30, 2017,the entirety of which is hereby incorporated by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to photoactivatable compounds and methodsof use thereof for identifying RNA transcripts that bind such compoundsand are thus druggable, methods of screening drug candidates, andmethods of determining drug binding sites and/or reactive site(s) on atarget RNA. The invention also provides methods for modulating thebiology of RNA transcripts to treat various diseases and conditions.

SEQUENCE LISTING

The instant application contains a Sequence Listing which has beensubmitted electronically in ASCII format and is hereby incorporated byreference in its entirety. Said ASCII copy, created on Nov. 30, 2018, isnamed 394457_003US_164432_SL_ST25.TXT and is 46,324 bytes in size.

BACKGROUND OF THE INVENTION

Ribonucleic acids (RNAs) have been conventionally considered meretransient intermediaries between genes and proteins, whereby aprotein-coding section of deoxyribonucleic acid (DNA) is transcribedinto RNA that is then translated into a protein. RNA was thought to lackdefined tertiary structure, and even where tertiary structure waspresent it was believed to be largely irrelevant to the RNA's functionas a transient messenger. This understanding has been challenged by therecognition that RNA, including non-coding RNA (ncRNA), plays amultitude of critical regulatory roles in the cell and that RNA can havecomplex, defined, and functionally-essential tertiary structure.

All endogenous mammalian diseases are ultimately mediated by thetranscriptome. Insofar as messenger mRNA (mRNA) is part of thetranscriptome, and all protein expression derives from mRNAs, there isthe potential to intervene in protein-mediated diseases by modulatingthe expression of the relevant protein and by, in turn, modulating thetranslation of the corresponding upstream mRNA. But mRNA is only a smallportion of the transcriptome: other transcribed RNAs also regulatecellular biology either directly by the structure and function of RNAstructures (e.g., ribonucleoproteins) as well as via protein expressionand action, including (but not limited to) miRNA, lncRNA, lincRNA,snoRNA, snRNA, scaRNA, piRNA, ceRNA, and pseudo-genes. Drugs thatintervene at this level have the potential of modulating any and allcellular processes. Existing therapeutic modalities such as antisenseRNA or siRNA, in most cases, have yet to overcome significant challengessuch as drug delivery, absorption, distribution to target organs,pharmacokinetics, and cell penetration. In contrast, small moleculeshave a long history of successfully surmounting these barriers and thesequalities, which make them suitable as drugs, are readily optimizedthrough a series of analogues to overcome such challeges. In sharpcontrast, there are no validated, general methods of screening smallmolecules for binding to RNA targets in general, much less inside cells.The application of small molecules as ligands for RNA that yieldtherapeutic benefit has received little to no attention from the drugdiscovery community.

Targeting the RNA transcriptome with small molecule modulatorsrepresents an untapped therapeutic approach to treat a variety ofRNA-mediated diseases. Accordingly, there remains a need to developsmall-molecule RNA modulators useful as therapeutic agents.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows structures of theophylline ligands with points ofattachment for the tethering groups.

FIG. 2 shows structures of tetracycline ligands with points ofattachment for the tethering groups.

FIG. 3 shows structures of triptycene ligands with points of attachmentfor the tethering groups.

FIG. 4 shows structures of triptycene ligands with points of attachmentfor the tethering groups. X═CH, H, or C—OH; Y═CH or N; R1, R2, R3=eachindependently selected from halo, —OH, —OMe, —NH₂, —NH-(optionallysubstituted C₁₋₁₀ aliphatic), optionally substituted C₁₋₁₀ aliphatic, orother described tethering groups. The modifier moiety may be attached atany position on R1, R₂, or R3, or at the other functional groups on theabove structures.

FIG. 5 shows structures of anthracene-maleimide Diels-Alder adductligands with points of attachment for the tethering groups. Note: Thecorresponding structures having the succinimido group in the oppositestereochemical orientation may also be prepared. Each R is independentlyselected from halo, —OH, —OMe, —NH₂, —NH-(optionally substituted C₁₋₁₀aliphatic), optionally substituted C₁₋₁₀ aliphatic, or other describedtethering groups. The modifier moiety may be attached at any position onR, or at the other functional groups on the above structures.

FIG. 6 shows structures of ribocil ligands with points of attachment forthe tethering groups.

FIG. 7 shows structures of SMN2 ligands with points of attachment forthe tethering groups.

FIG. 8 shows structures of linezolid and tedizolid ligands with pointsof attachment for the tethering groups.

FIG. 9 shows structures of exemplary click-ready groups.

FIG. 10 shows exemplary tethering groups for linking RNA ligands andmodifying moieties.

FIG. 11 shows further examples of tethering groups.

FIG. 12 shows further examples of tethering groups.

FIG. 13 shows further examples of tethering groups.

FIG. 14 shows further examples of tethering groups.

FIG. 15 shows further examples of tethering groups.

FIG. 16 shows further examples of tethering groups.

FIG. 17 shows further examples of tethering groups.

FIG. 18 shows reaction schemes for accessing several theophylline smallmolecule ligands that include attachment points for the tethering group.

FIG. 19 shows reaction schemes for accessing several theophylline smallmolecule ligands that include attachment points for the tethering group.

FIG. 20 shows reaction schemes for accessing several theophylline smallmolecule ligands that include attachment points for the tethering group.

FIG. 21 shows reaction schemes for accessing several theophylline smallmolecule ligands that include attachment points for the tethering group.

FIG. 22 shows reaction schemes for accessing several tetracycline smallmolecule ligands that include attachment points for the tethering group.

FIG. 23 shows reaction schemes for accessing several tetracycline smallmolecule ligands that include attachment points for the tethering group.

FIG. 24 shows reaction schemes for accessing several tetracycline smallmolecule ligands that include attachment points for the tethering group.

FIG. 25 shows reaction schemes for accessing several tetracycline smallmolecule ligands that include attachment points for the tethering group.

FIG. 26 shows reaction schemes for accessing several triptycene smallmolecule ligands that include attachment points for the tethering group.

FIG. 27 shows reaction schemes for accessing several triptycene smallmolecule ligands that include attachment points for the tethering group.

FIG. 28 shows reaction schemes for accessing several triptycene smallmolecule ligands that include attachment points for the tethering group.

FIG. 29 shows reaction schemes for accessing several triptycene smallmolecule ligands that include attachment points for the tethering group.

FIG. 30 shows reaction schemes for accessing several triptycene smallmolecule ligands that include attachment points for the tethering group.

FIG. 31 shows reaction schemes for accessing several triptycene smallmolecule ligands that include attachment points for the tethering group.

FIG. 32 shows reaction schemes for accessing several triptycene smallmolecule ligands that include attachment points for the tethering group.

FIG. 33 shows reaction schemes for accessing several triptycene smallmolecule ligands that include attachment points for the tethering group.

FIG. 34 shows reaction schemes for accessing several tetracycline smallmolecule ligands that include a tethering group and modifying moiety.

FIG. 35 shows reaction schemes for accessing several triptycene smallmolecule ligands that include a tethering group and modifying moiety.

FIG. 36 shows a synthetic route for compound ARK-132.

FIG. 37 shows a synthetic route for compound ARK-134.

FIG. 38 shows a synthetic route for compounds ARK-135 and ARK-136.

FIG. 39 shows a synthetic route for compound ARK-188.

FIG. 40 shows a synthetic route for compound ARK-190.

FIG. 41 shows a synthetic route for compound ARK-191.

FIG. 42 shows a synthetic route for compound ARK-195.

FIG. 43 shows a synthetic route for compound ARK-197.

FIG. 44 shows a synthetic route for compounds based on the ribocilscaffold.

FIG. 45 shows photochemical reactions of NAz photoprobes which contain a(hetero)aroyl azide, as well as C8 modification reactions of the nitreneintermediate with guanosines.

FIG. 46 shows several riboswitch/aptamer-ligand pairs useful as positivecontrol model systems for assay development in accordance with thepresent invention. The PreQ₁ ligand and sequence are disclosed in NatStruct Mol Biol 16, 343-344 (2009), which is hereby incorporated byreference. The TPP ligand and sequence are disclosed in Nature 441,1167-1171 (2006) and Structure 14, 1459-1468 (2006), each of which ishereby incorporated by reference.

FIG. 47 shows surface plasmon resonance (SPR) results with theriboswitch/aptamer ligand pairs. While compound 1b (compound I-1,ARK-139) binds Aptamer 21, it is known not to bind a mutant sequence,Aptamer 21-E (data not shown).

FIG. 48 shows ARK-139 binding to Aptamer 21 by SPR; calculated K_(D)=568nM by SPR. Binding was also confirmed by SEC-MS (data not shown)

FIG. 49 shows SHAPE reactivity results from the use of SHAPE-MaP onAptamer 21. Higher peak values signify increased solvent exposure andreactivity of individual nucleotides of the aptamer, with and withoutthe presence of the ligand I-1 (ARK-139).

FIG. 50 shows results from the use of SHAPE-MaP on Aptamer 21-E(bottom). Higher peak values signify increased solvent exposure andreactivity of individual nucleotides of the aptamer, with and withoutthe presence of the ligand I-1 (ARK-139). As can be seen, the presenceof I-1 caused almost no alteration in the SHAPE reactivity, suggestingweak binding of I-1 to Aptamer 21-E.

FIG. 51 shows the predicted binding mode of photoprobe ARK-547 toAptamer 21. As the model shows, the predicted binding mode accommodatesthe linker and photoactivatable group.

FIG. 52 shows gel results of a PEARL-seq reverse transcriptase pausingassay. The transcriptase pauses at covalently modified nucleotides,leading to accumulation of shortened sequences. ARK-547 treatment leadsto production of such shortened sequences of particular lengths,indicating that certain nucleotides are more likely to be covalentlymodified than others. NAI leads to modification at moreaccessbile/reactive nucleotides, leading to less selectivity andproducing numerous shortened sequences.

FIG. 53 shows reverse transcriptase (RT) pausing results with Aptamer 21and PreQ1 RNA. The Aptamer 21 diazirine probe ARK-547 shows specific andUV-dependent cross-linking with Apt21 RNA; PreQ1 probe does not showcross-linking to Apt21 or PreQ1 RNA. Conditions: 1 uM RNA, 10 uM probe,9 uM PreQ1 probe, 20 mM TrisHCl pH 8, 100 mM KCl, 3 mM MgCl₂, 37° C. for30 min, shielded from light, UV irradiation (˜360 nm) for 3 indicatedtime at room temperature.

FIG. 54 shows screening results for additional compounds forcross-linking of Aptamer 21. Conditions: 1 μM refolded RNA, 10 μMcompound, 20 mM TrisHCl pH 8, 100 mM KCl, 3 mM MgCl2, 2.5% DMSO.Reactions were incubated for 30 min at 37° C. shielded from light,followed by 5 min irradiation with 360 nm light at room temperature inFisher photo-crosslinker.

FIG. 55 shows models of Aptamer 21 vs. Aptamer 21-E binding to I-1.

FIG. 56 shows SPR data for I-1 (ARK-139) binding to Aptamer 21. ARK-139did not bind to Aptamer 21-E (data not shown). The calculated K_(d) was420 nM.

FIG. 57 shows a gel assay in which Aptamer 21 and Aptamer 21-E wereincubated with a biotin-photoaffinity bifunctional probe ARK-670,cross-linked, and then captured on streptavidin beads. Only the Aptamer21 RNA showed significant pull-down. shows results of sequencing ofcross-linked Aptamer 21 after treatment with ARK-547 measuring MaPsignal at positions 43 and 60, and selective drop-off at position 60.Combining with streptavidin capture will identify binding sites from amixture of RNA.

FIGS. 58A and 58B show LC-MS results with Aptamer 21. ARK-547 andARK-581 0 showed 5% and 10% covalent modification of the RNA,respectively.

FIG. 59 shows reverse transcriptase (RT) pausing assay results usingbifunctional photoactivatable compounds.

FIG. 60 shows biotin pull-down experiment results. Steps: Cross-linkedbiotin-diazirine probe (ARK-579) to RNA; Captured on streptavidinmagnetic beads; Performed RT on beads; Base-hydrolyzed RNA to elutecDNA; Ran on gel.

FIG. 61A and 61B show RT pausing and mutation rate results.Photo-crosslinking of Aptamer 21 and photoprobe ARK-547 revealed thatARK-547 does not bind to negative control Aptamer 21-E and yields nophotoadduct. Reverse transcriptase (RT) pausing was maximal at nt 59,consistent with predicted binding mode. Sites of normalized mutationalrate were also consistent with the ARK-547 binding mode.

FIG. 62 shows the structures of I-14 (ARK-729) and I-15 (ARK-816) andlabeling of RNA-photoprobe adducts via a Cu-free click reaction usingthese compounds. Lanes 1-5 were run with different combinations ofdenaturant and Cu-free click reaction conditions. Lane 1: nodenaturant/10 mM Tris, 1 mM EDTA, pH 8.0, 37° C. click conditions; Lane2: no denaturant/10 mM Tris, 10 mM EDTA, pH 8.0, 65° C. clickconditions; Lane 3: 6 M Urea denaturant/10 mM Tris, 10 mM EDTA, pH 8.0,65° C. click conditions; Lane 4: 90% formamide denaturant/10 mM Tris, 10mM EDTA, pH 8.0, 65° C. click conditions; Lane 5: 1× TBE-Urea buffer,65° C. Aptamer 21 was treated with ARK-729 or ARK-816, then wassubjected to UV photocrosslinking. The resulting photoadducts were thentreated with a Cy7-DBCO conjugate under the indicated conditions.Performing the Cu-free click reaction at 65° C. without any additivesenabled detection of the Aptamer 21-probe photoadducts by Cy7fluorescence.

FIG. 63 shows results for competition experiments between Aptamer 21photoprobes and RNA-binding ligands. Aptamer 21 was either incubatedwith probe alone (ARK-581) or probe plus a 10-fold excess of RNA-bindingligand. Only SPR-active compounds ARK-139 and ARK-852 efficientlyinhibited photocrosslinking of ARK-581 to Aptamer 21.

FIG. 64 shows RT pausing results for photocrosslinking of structurallydistinct Aptamer 21 ligands to Aptamer 21.

FIG. 65 shows RT pausing results for a competition assay. Both ARK-852and ARK-139 inhibit the photocrosslinking of probes to Aptamer 21.

FIG. 66 shows RT pausing results relating to photocrosslinking ofchemical probes to Aptamer 21.

FIG. 67A and FIG. 67B shows photocrosslinking of ARK-670 to Aptamer 21,Aptamer 21-E, or a mixture of Aptamer 21 and four other RNAs. The RTpausing signal from probe adducts was specific for Aptamer 21 andincreased in strength after bead enrichment of crosslinked RNA.

FIG. 68 shows selective enrichment of Aptamer 21 by ARK-670 in thepresence of other RNA squences. Cross-linking of ARK-670 to a mixture ofAptamer 21 and four other RNAs was followed by avidin bead enrichment ofcross-linked RNA and sequencing. Sequencing analysis showed that onlyAptamer 21 was enriched by ARK-670, which suggests that ARK-670 binds toAptamer 21 and cross-links selectively in a proximity-driven manner.

FIG. 69 shows RT pausing data from click-biotinylated probes afterenrichment. Crosslinking of Aptamer 21 or Aptamer 21-E to ARK-729(phenylazide probe), ARK-2058 (phenylazide warhead-only control),ARK-816 (diazirine probe), ARK-2059 (diazirine warhead-only control) orDMSO was followed by enrichment on avidin beads and sequencing. Theprobes ARK-729 and ARK-816 showed RT pausing peaks specific to Aptamer21.

FIG. 70 shows a cartoon mapping the locations of RT pausing peaks onAptamer 21's sequence.

FIG. 71 shows RT pausing on Aptamer 21 spiked into PolyA+ RNA extract.Crosslinking of ARK-816 (diazirine probe) or ARK-2059 (diazirinewarhead-only control) to Aptamer 21 spiked into a polyA+ RNA extract andthe RT pausing ratio was measured by sequencing. Peaks specific to theARK-816 probe were observed at the same positions as for isolatedAptamer 21.

FIG. 72 shows enrichment analysis of Aptamer 21 from a PolyA+ RNAextract. Aptamer 21 was spiked into polyA+ RNA extract and then themixture was crosslinked to ARK-816 (diazirine probe) and ARK-2059(warhead-only control) and crosslinked RNA was enriched by avidincapture. Specific enrichment of sequences by the probe as compared tothe warhead-only control determined by next-generation sequencing.Enrichment of the sites of probe-specific RT pausing on Aptamer 21 wasobserved.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS 1. General Description ofCertain Embodiments of the Invention; Definitions

RNA Targets and Association with Diseases and Disorders

The vast majority of molecular targets that have been addressedtherapeutically are proteins. However, it is now understood that avariety of RNA molecules play important regulatory roles in both healthyand diseased cells. While only 1-2% of the human genome codes forproteins, it is now known that the majority of the genome is transcribed(Carninci et al., Science 309:1559-1563; 2005). Thus, the noncodingtranscripts (the noncoding transcriptome) represent a large group of newtherapeutic targets. Noncoding RNAs such as microRNA (miRNA) and longnoncoding RNA (lncRNA) regulate transcription, splicing, mRNAstability/decay, and translation. In addition, the noncoding regions ofmRNA such as the 5′ untranslated regions (5′ UTR), the 3′ UTR, andintrons can play regulatory roles in affecting mRNA expression levels,alternative splicing, translational efficiency, and mRNA and proteinsubcellular localization. RNA secondary and tertiary structures arecritical for these regulatory activities.

Remarkably, GWAS studies have shown that there are far more singlenucleotide polymorphisms (SNPs) associated with human disease in thenoncoding transcriptome relative to the coding transcripts (Maurano etal., Science 337:1190-1195; 2012). Therefore, the therapeutic targetingof noncoding RNAs and noncoding regions of mRNA can yield novel agentsto treat to previously intractable human diseases.

Current therapeutic approaches to interdict mRNA require methods such asgene therapy (Naldini, Nature 2015, 526, 351-360), genome editing (Coxet al., Nature Medicine 2015, 21, 121-131), or a wide range ofoligonucleotide technologies (antisense, RNAi, etc.) (Bennett & Swayze,Annu. Rev. Pharmacol. Toxicol. 2010, 50, 259-293). Oligonucleotidesmodulate the action of RNA via canonical base/base hybridization. Theappeal of this approach is that the basic pharmacophore of anoligonucleotide can be defined in a straightforward fashion from thesequence subject to interdiction. Each of these therapeutic modalitiessuffers from substantial technical, clinical, and regulatory challenges.Some limitations of oligonucleotides as therapeutics (e.g. anti sense,RNAi) include unfavorable pharmacokinetics, lack of oralbioavailability, and lack of blood-brain-barrier penetration, with thelatter precluding delivery to the brain or spinal cord after parenteraldrug administration for the treatment of neurological diseases. Inaddition, oligonucleotides are not taken up effectively into solidtumors without a complex delivery system such as lipid nanoparticles.Lastly, a vast majority of the oligonucleotides that are taken up intocells and tissues remain in a non-functional compartment such asendosomes, and only a small fraction of the material escapes to gainaccess to the cytosol and/or nucleus where the target is located.

“Traditional” small molecules can be optimized to exhibit excellentabsorption from the gut, excellent distribution to target organs, andexcellent cell penetration. The use of “traditional” (i.e.,“Lipinski-compliant” (Lipinski et al., Adv. Drug Deliv. Rev. 2001, 46,3-26) small molecules with favorable drug properties that bind andmodulate the activity of a target RNA would solve many of the problemsnoted above.

In one aspect, the present invention provides a method of identifyingthe identity or structure of a binding or active site to which a smallmolecule binds in a target RNA, comprising the steps of i) contactingthe target RNA with a disclosed compound and ii) analyzing the resultsby an assay disclosed herein, optionally in combination with acomputational method. In some embodiments, the target RNA is selectedfrom a mRNA or a noncoding RNA. In some embodiments, the target RNA isan aptamer or riboswitch. In some embodiments, the RNA is the FMNriboswitch, PreQi, or Aptamer 21. In some embodiments, the assayidentifies the location in the primary sequence of the binding site(s)on the target RNA.

Targeting mRNA

Within mRNAs, noncoding regions can affect the level of mRNA and proteinexpression. Briefly, these include IRES and upstream open reading frames(uORF) that affect translation efficiency, intronic sequences thataffect splicing efficiency and alternative splicing patterns, 3′ UTRsequences that affect mRNA and protein localization, and elements thatcontrol mRNA decay and half-life. Therapeutic modulation of these RNAelements can have beneficial effects. Also, mRNAs may contain expansionsof simple repeat sequences such as trinucleotide repeats. These repeatexpansion containing RNAs can be toxic and have been observed to drivedisease pathology, particularly in certain neurological andmusculoskeletal diseases (see Gatchel & Zoghbi, Nature Rev. Gen. 2005,6, 743-755). In addition, splicing can be modulated to skip exons havingmutations that introduce stop codons in order to relieve prematuretermination during translation.

Small molecules can be used to modulate splicing of pre-mRNA fortherapeutic benefit in a variety of settings. One example is spinalmuscular atrophy (SMA). SMA is a consequence of insufficient amounts ofthe survival of motor neuron (SMN) protein. Humans have two versions ofthe SMN gene, SMN1 and SMN2. SMA patients have a mutated SMN1 gene andthus rely solely on SMN2 for their SMN protein. The SMN2 gene has asilent mutation in exon 7 that causes inefficient splicing such thatexon 7 is skipped in the majority of SMN2 transcripts, leading to thegeneration of a defective protein that is rapidly degraded in cells,thus limiting the amount of SMN protein produced from this locus. Asmall molecule that promotes the efficient inclusion of exon 7 duringthe splicing of SMN2 transcripts would be an effective treatment for SMA(Palacino et al., Nature Chem. Biol., 2015, 11, 511-517). Accordingly,in one aspect, the present invention provides a method of identifying asmall molecule that modulates the splicing of a target pre-mRNA to treata disease or disorder, comprising the steps of: screening one or moredisclosed compounds for binding to the target pre-mRNA; and analyzingthe results by an RNA binding assay disclosed herein. In someembodiments, the pre-mRNA is an SMN2 transcript. In some embodiments,the disease or disorder is spinal muscular atrophy (SMA).

Even in cases in which defective splicing does not cause the disease,alteration of splicing patterns can be used to correct the disease.Nonsense mutations leading to premature translational termination can beeliminated by exon skipping if the exon sequences are in-frame. This cancreate a protein that is at least partially functional. One example ofthe use of exon skipping is the dystrophin gene in Duchenne musculardystrophy (DMD). A variety of different mutations leading to prematuretermination codons in DMD patients can be eliminated by exon skippingpromoted by oligonucleotides (reviewed in Fairclough et al., Nature Rev.Gen., 2013, 14, 373-378). Small molecules that bind RNA structures andaffect splicing are expected to have a similar effect. Accordingly, inone aspect, the present invention provides a method of identifying asmall molecule that modulates the splicing pattern of a target pre-mRNAto treat a disease or disorder, comprising the steps of: screening oneor more disclosed compounds for binding to the target pre-mRNA; andanalyzing the results by an RNA binding assay disclosed herein. In someembodiments, the pre-mRNA is a dystrophin gene transcript. In someembodiments, the small molecule promotes exon skipping to eliminatepremature translational termination. In some embodiments, the disease ordisorder is Duchenne muscular dystrophy (DMD).

Lastly, the expression of an mRNA and its translation products could beaffected by targeting noncoding sequences and structures in the 5′ and3′ UTRs. For instance, RNA structures in the 5′ UTR can affecttranslational efficiency. RNA structures such as hairpins in the 5′ UTRhave been shown to affect translation. In general, RNA structures arebelieved to play a critical role in translation of mRNA. Two examples ofthese are internal ribosome entry sites (IRES) and upstream open readingframes (uORF) that can affect the level of translation of the main openreading frame (Komar and Hatzoglou, Frontiers Oncol. 5:233, 2015;Weingarten-Gabbay et al., Science 351:pii:aad4939, 2016; Calvo et al.,Proc. Natl. Acad. Sci. USA 106:7507-7512; Le Quesne et al., J. Pathol.220:140-151, 2010; Barbosa et al., PLOS Genetics 9:e10035529, 2013). Forexample, nearly half of all human mRNAs have uORFs, and many of thesereduce the translation of the main ORF. Small molecules targeting theseRNAs could be used to modulate specific protein levels for therapeuticbenefit. Accordingly, in one aspect, the present invention provides amethod of producing a small molecule that modulates the expression ortranslation efficiency of a target pre-mRNA or mRNA to treat a diseaseor disorder, comprising the steps of: screening one or more disclosedcompounds for binding to the target pre-mRNA or mRNA; and analyzing theresults by an RNA binding assay disclosed herein. In some embodiments,the small molecule binding site is a 5′ UTR, internal ribosome entrysite, or upsteam open reading frame.

Targeting Regulatory RNA

The largest set of RNA targets is RNA that is transcribed but nottranslated into protein, termed “non-coding RNA”. Non-coding RNA ishighly conserved and the many varieties of non-coding RNA play a widerange of regulatory functions. The term “non-coding RNA,” as usedherein, includes but is not limited to micro-RNA (miRNA), longnon-coding RNA (lncRNA), long intergenic non-coding RNA (lincRNA),Piwi-interacting RNA (piRNA), competing endogenous RNA (ceRNA), andpseudo-genes. Each of these sub-categories of non-coding RNA offers alarge number of RNA targets with significant therapeutic potential.Accordingly, in some embodiments, the present invention provides methodsof treating a disease mediated by non-coding RNA. In some embodiments,the disease is caused by a miRNA, lncRNA, lincRNA, piRNA, ceRNA, orpseudo-gene. In another aspect, the present invention provides a methodof producing a small molecule that modulates the activity of a targetnon-coding RNA to treat a disease or disorder, comprising the steps of:screening one or more disclosed compounds for binding to the targetnon-coding RNA; and analyzing the results by an RNA binding assaydisclosed herein. In some embodiments, the target non-coding RNA is amiRNA, lncRNA, lincRNA, piRNA, ceRNA, or pseudo-gene.

miRNA are short double-strand RNAs that regulate gene expression (seeElliott & Ladomery, Molecular Biology of RNA, 2^(nd) Ed.). Each miRNAcan affect the expression of many human genes. There are nearly 2,000miRNAs in humans. These RNAs regulate many biological processes,including cell differentiation, cell fate, motility, survival, andfunction. miRNA expression levels vary between different tissues, celltypes, and disease settings. They are frequently aberrantly expressed intumors versus normal tissue, and their activity may play significantroles in cancer (for reviews, see Croce, Nature Rev. Genet. 10:704-714,2009; Dykxhoorn Cancer Res. 70:6401-6406, 2010). miRNAs have been shownto regulate oncogenes and tumor suppressors and themselves can act asoncogenes or tumor suppressors. Some have been shown to promoteepithelial-mesenchymal transition (EMT) and cancer cell invasiveness andmetastasis. In the case of oncogenic miRNAs, their inhibition could bean effective anti-cancer treatment. Accordingly, in one aspect, thepresent invention provides a method of producing a small molecule thatmodulates the activity of a target miRNA to treat a disease or disorder,comprising the steps of: screening one or more disclosed compounds forbinding to the target miRNA; and analyzing the results by an RNA bindingassay disclosed herein. In some embodiments, the miRNA regulates anoncogene or tumor suppressor, or acts as an oncogene or tumorsuppressor. In some embodiments, the disease is cancer. In someembodiments, the cancer is a solid tumor.

There are multiple oncogenic miRNA that could be therapeuticallytargeted including miR-155, miR-17˜92, miR-19, miR-21, and miR-10b (seeStahlhut & Slack, Genome Med. 2013, 5, 111). miR-155 plays pathologicalroles in inflammation, hypertension, heart failure, and cancer. Incancer, miR-155 triggers oncogenic cascades and apoptosis resistance, aswell as increasing cancer cell invasiveness. Altered expression ofmiR-155 has been described in multiple cancers, reflecting staging,progress and treatment outcomes. Cancers in which miR-155over-expression has been reported are breast cancer, thyroid carcinoma,colon cancer, cervical cancer, and lung cancer. It is reported to play arole in drug resistance in breast cancer. miR-17˜92 (also calledOncomir-1) is a polycistronic 1 kb primary transcript comprising miR-17,20a, 18a, 19a, 92-1 and 19b-1. It is activated by MYC. miR-19 alters thegene expression and signal transduction pathways in multiplehematopoietic cells, and it triggers leukemogenesis and lymphomagenesis.It is implicated in a wide variety of human solid tumors andhematological cancers. miR-21 is an oncogenic miRNA that reduces theexpression of multiple tumor suppressors. It stimulates cancer cellinvasion and is associated with a wide variety of human cancersincluding breast, ovarian, cervix, colon, lung, liver, brain, esophagus,prostate, pancreas, and thyroid cancers. Accordingly, in someembodiments of the methods described above, the target miRNA is selectedfrom miR-155, miR-17˜92, miR-19, miR-21, or miR-10b. In someembodiments, the disease or disorder is a cancer selected from breastcancer, ovarian cancer, cervical cancer, thyroid carcinoma, coloncancer, liver cancer, brain cancer, esophageal cancer, prostate cancer,lung cancer, leukemia, or lymph node cancer. In some embodiments, thecancer is a solid tumor.

Beyond oncology, miRNAs play roles in many other diseases includingcardiovascular and metabolic diseases (Quiant and Olson, J. Clin.Invest. 123:11-18, 2013; Olson, Science Trans. Med. 6: 239ps3, 2014;Baffy, J. Clin. Med. 4:1977-1988, 2015).

Many mature miRNAs are relatively short in length and thus may lacksufficient folded, thrtee-dimensional structure to be targeted by smallmolecules. However, it is believed that the levels of such miRNA couldbe reduced by small molecules that bind the primary transcript or thepre-miRNA to block the biogenesis of the mature miRNA. Accordingly, insome embodiments of the methods described above, the target miRNA is aprimary transcript or pre-miRNA.

lncRNA are RNAs of over 200 nucleotides (nt) that do not encode proteins(see Rinn & Chang, Ann. Rev. Biochem. 2012, 81, 145-166; (for reviews,see Morris and Mattick, Nature Reviews Genetics 15:423-437, 2014;Mattick and Rinn, Nature Structural & Mol. Biol. 22:5-7, 2015; Iyer etal., Nature Genetics 47(:199-208, 2015)). They can affect the expressionof the protein-encoding mRNAs at the level of transcription, splicingand mRNA decay. Considerable research has shown that lncRNA can regulatetranscription by recruiting epigenetic regulators that increase ordecrease transcription by altering chromatin structure (e.g., Holoch andMoazed, Nature Reviews Genetics 16:71-84, 2015). lncRNAs are associatedwith human diseases including cancer, inflammatory diseases,neurological diseases and cardiovascular disease (for instance, Presnerand Chinnaiyan, Cancer Discovery 1:391-407, 2011; Johnson, Neurobiologyof Disease 46:245-254, 2012; Gutscher and Diederichs, RNA Biology9:703-719, 2012; Kumar et al., PLOS Genetics 9:e1003201, 2013; van deVondervoort et al., Frontiers in Molecular Neuroscience, 2013; Li etal., Int. J. Mol. Sci. 14:18790-18808, 2013). The targeting of lncRNAcould be done to up-regulate or down-regulate the expression of specificgenes and proteins for therapeutic benefit (e.g., Wahlestedt, NatureReviews Drug Discovery 12:433-446, 2013; Guil and Esteller, NatureStructural & Mol. Biol. 19:1068-1075, 2012). In general, lncRNA areexpressed at a lower level relative to mRNAs. Many lncRNAs arephysically associated with chromatin (Werner et al., Cell Reports 12,1-10, 2015) and are transcribed in close proximity to protein-encodinggenes. They often remain physically associated at their site oftranscription and act locally, in cis, to regulate the expression of aneighboring mRNA. The mutation and dysregulation of lncRNA is associatedwith human diseases; therefore, there are a multitude of lncRNAs thatcould be therapeutic targets. Accordingly, in some embodiments of themethods described above, the target non-coding RNA is a lncRNA. In someembodiments, the lncRNA is associated with a cancer, inflammatorydisease, neurological disease, or cardiovascular disease.

lncRNAs regulate the expression of protein-encoding genes, acting atmultiple different levels to affect transcription, alternative splicingand mRNA decay. For example, lncRNA has been shown to bind to theepigenetic regulator PRC2 to promote its recruitment to genes whosetranscription is then repressed via chromatin modification. lncRNA mayform complex structures that mediate their association with variousregulatory proteins. A small molecule that binds to these lncRNAstructures could be used to modulate the expression of genes that arenormally regulated by an individual lncRNA.

One examplary target lncRNA is HOTAIR, an lncRNA expressed from the HoxClocus on human chromosome 12. Is expression level is low (˜100 RNAcopies per cell). Unlike many lncRNAs, HOTAIR can act in trans to affectthe expression of distant genes. It binds the epigenetic repressor PRC2as well as the LSD1/CoREST/REST complex, another repressive epigeneticregulator (Tsai et al., Science 329, 689-693, 2010). HOTAIR is a highlystructured RNA with over 50% of its nucleotides being involved in basepairing. It is frequently dysregulated (often up-regulated) in varioustypes of cancer (Yao et al., Int. J. Mol. Sci. 15:18985-18999, 2014;Deng et al., PLOS One 9:e110059, 2014). Cancer patients with highexpression levels of HOTAIR have a significantly poorer prognosis,compared with those with low expression levels. HOTAIR has been reportedto be involved in the control of apoptosis, proliferation, metastasis,angiogenesis, DNA repair, chemoresistance and tumor cell metabolism. Itis highly expressed in metastatic breast cancers. High levels ofexpression in primary breast tumors are a significant predictor ofsubsequent metastasis and death. HOTAIR also has been reported to beassociated with esophageal squamous cell carcinoma, and it is aprognostic factor in colorectal cancer, cervical cancer, gastric cancerand endometrial carcinoma. Therefore, HOTAIR-binding small molecules arenovel anti-cancer drug candidates. Accordingly, in some embodiments ofthe methods described above, the target non-coding RNA is HOTAIR. Insome embodiments, the disease or disorder is breast cancer, esophagealsquamous cell carcinoma, colorectal cancer, cervical cancer, gastriccancer, or endometrial carcinoma.

Another potential cancer target among lncRNA is MALAT-1(metastasis-associated lung adenocarcinoma transcript 1), also known asNEAT2 (nuclear-enriched abundant transcript 2) (Gutschner et al., CancerRes. 73:1180-1189, 2013; Brown et al., Nat. Structural & Mol. Biol.21:633-640, 2014). It is a highly conserved 7 kb nuclear lncRNA that islocalized in nuclear speckles. It is ubiquitously expressed in normaltissues, but is up-regulated in many cancers. MALAT-1 is a predictivemarker for metastasis development in multiple cancers including lungcancer. It appears to function as a regulator of gene expression,potentially affecting transcription and/or splicing. MALAT-1 knockoutmice have no phenotype, indicating that it has limited normal function.However, MALAT-1-deficient cancer cells are impaired in migration andform fewer tumors in a mouse xenograft tumor models. Antisenseoligonucleotides (ASO) blocking MALAT-1 prevent metastasis formationafter tumor implantation in mice. Some mouse xenograft tumor model dataindicates that MALAT-1 knockdown by ASOs may inhibit both primary tumorgrowth and metastasis. Thus, a small molecule targeting MALAT-1 isexptected to be effective in inhibiting tumor growth and metastasis.Accordingly, in some embodiments of the methods described above, thetarget non-coding RNA is MALAT-1. In some embodiments, the disease ordisorder is a cancer in which MALAT-1 is upregulated, such as lungcancer.

In some embodiments, the present invention provides a method of treatinga disease or disorder mediated by non-coding RNA (such as HOTAIR orMALAT-1), comprising the step of administering to a patient in needthereof a compound of the present invention. Such compounds aredescribed in detail herein.

Targeting Toxic RNA (Repeat RNA)

Simple repeats in mRNA often are associated with human disease. Theseare often, but not exclusively, repeats of three nucleotides such as CAG(“triplet repeats”) (for reviews, see Gatchel and Zoghbi, Nature ReviewsGenetics 6:743-755, 2005; Krzyzosiak et al., Nucleic Acids Res.40:11-26, 2012; Budworth and McMurray, Methods Mol. Biol. 1010:3-17,2013). Triplet repeats are abundant in the human genome, and they tendto undergo expansion over generations. Approximately 40 human diseasesare associated with the expansion of repeat sequences. Diseases causedby triplet expansions are known as Triplet Repeat Expansion Diseases(TRED). Healthy individuals have a variable number of triplet repeats,but there is a threshold beyond which a higher repeat number causesdisease. The threshold varies in different disorders. The triplet repeatcan be unstable. As the gene is inherited, the number of repeats mayincrease, and the condition may be more severe or have an earlier onsetfrom generation to generation. When an individual has a number ofrepeats in the normal range, it is not expected to expand when passed tothe next generation. When the repeat number is in the premutation range(a normal, but unstable repeat number), then the repeats may or may notexpand upon transmission to the next generation. Normal individuals whocarry a premutation do not have the condition, but are at risk of havinga child who has inherited a triplet repeat in the full mutation rangeand who will be affected. TREDs can be autosomal dominant, autosomalrecessive or X-linked. The more common triplet repeat disorders areautosomal dominant.

The repeats can be in the coding or noncoding portions of the mRNA. Inthe case of repeats within noncoding regions, the repeats may lie in the5′ UTR, introns, or 3′ UTR sequences. Some examples of diseases causedby repeat sequences within coding regions are shown in Table 1.

TABLE 1 Repeat Expansion Diseases in Which the Repeat Resides in theCoding Regions of mRNA Normal Disease repeat repeat Disease Gene Repeatnumber number HD HTT CAG 6-35 (SEQ ID 36-250 (SEQ NO: 1) ID NO: 8) DRPLAATN1 CAG 6-35 (SEQ ID 49-88 (SEQ NO: 1) ID NO: 9) SBMA AR CAG 9-36 (SEQID 38-62 (SEQ NO: 2) ID NO: 10) SCA1 ATXN1 CAG 6-35 (SEQ ID 49-88 (SEQNO: 1) ID NO: 9) SCA2 ATXN2 CAG 14-32 (SEQ 33-77 (SEQ ID NO: 3) ID NO:11) SCA3 ATXN3 CAG 12-40 (SEQ 55-86 (SEQ ID NO: 4) ID NO: 12) SCA6CACNA1A CAG 4-18 (SEQ ID 21-30 (SEQ NO: 5) ID NO: 13) SCA7 ATXN7 CAG7-17 (SEQ ID 38-120 (SEQ NO: 6) ID NO: 14) SCA17 TBP CAG 25-42 (SEQ47-63 (SEQ ID NO: 7) ID NO: 15)

Some examples of diseases caused by repeat sequences within noncodingregions of mRNA are shown in Table 2.

TABLE 2 Repeat Expansion Diseases in Which the Repeat Resides in theNoncoding Regions of mRNA Normal Disease Repeat repeat repeat DiseaseGene Repeat location number number Fragile X FMR1 CGG 5′ UTR 6-53 (SEQID ≥230 NO: 16) DM1 DMPK CTG 3′ UTR 5-37 (SEQ ID ≥50 NO: 17) FRDA FXNGAA Intron 7-34 (SEQ ID ≥100 NO: 18) SCA8 ATXN8 CTG Noncoding 16-37 (SEQ110-250 antisense ID NO: 19) (SEQ ID NO: 22) SCA10 ATXN10 ATTCT Intron9-32 (SEQ ID 800-4500 NO: 20) (SEQ ID NO: 23) SCA12 PPP2R2B CAG 5′ UTR7-28 (SEQ ID 66-78 (SEQ NO: 21) ID NO: 24) C9FTD/ALS C9orf72 GGGGCCIntron ~30 100s

The toxicity that results from the repeat sequence can be directconsequence of the action of the toxic RNA itself, or, in cases in whichthe repeat expansion is in the coding sequence, due to the toxicity ofthe RNA and/or the aberrant protein. The repeat expansion RNA can act bysequestering critical RNA-binding proteins (RBP) into foci. One exampleof a sequestered RBP is the Muscleblind family protein MBNL1.Sequestration of RBPs leads to defects in splicing as well as defects innuclear-cytoplasmic transport of RNA and proteins. Sequestration of RBPsalso can affect miRNA biogenesis. These perturbations in RNA biology canprofoundly affect neuronal function and survival, leading to a varietyof neurological diseases.

Repeat sequences in RNA form secondary and tertiary structures that bindRBPs and affect normal RNA biology. One specific example disease ismyotonic dystrophy (DM1; dystrophia myotonica), a common inherited formof muscle disease characterized by muscle weakness and slow relaxationof the muscles after contraction (Machuca-Tzili et al., Muscle Nerve32:1-18, 2005). It is caused by a CUG expansion in the 3′ UTR of thedystrophia myotonica protein kinase (DMPK) gene. This repeat-containingRNA causes the misregulation of alternative splicing of severaldevelopmentally regulated transcripts through effects on the splicingregulators MBNL1 and the CUG repeat binding protein (CELF1) (Wheeler etal., Science 325:336-339, 2009). Small molecules that bind the CUGrepeat within the DMPK transcript would alter the RNA structure andprevent focus formation and alleviate the effects on these spicingregulators. Fragile X Syndrome (FXS), the most common inherited form ofmental retardation, is the consequence of a CGG repeat expansion withinthe 5′ UTR of the FMR1 gene (Lozano et al., Intractable Rare Dis. Res.3:134-146, 2014). FMRP is critical for the regulation of translation ofmany mRNAs and for protein trafficking, and it is an essential proteinfor synaptic development and neural plasticity. Thus, its deficiencyleads to neuropathology. A small molecule targeting this CGG repeat RNAmay alleviate the suppression of FMR1 mRNA and FMRP protein expression.Another TRED having a very high unmet medical need is Huntington'sdisease (HD). HD is a progressive neurological disorder with motor,cognitive, and psychiatric changes (Zuccato et al., Physiol Rev.90:905-981, 2010). It is characterized as a poly-glutamine or polyQdisorder since the CAG repeat within the coding sequence of the HTT geneleads to a protein having a poly-glutamine repeat that appears to havedetrimental effects on transcription, vesicle trafficking, mitochondrialfunction, and proteasome activity. However, the HTT CAG repeat RNAitself also demonstrates toxicity, including the sequestration of MBNL1protein into nuclear inclusions. One other specific example is theGGGGCC repeat expansion in the C9orf72 (chromosome 9 open reading frame72) gene that is prevalent in both familial frontotemporal dementia(FTD) and amyotrophic lateral sclerosis (ALS) (Ling et al., Neuron79:416-438, 2013; Haeusler et al., Nature 507:195-200, 2014). The repeatRNA structures form nuclear foci that sequester critical RNA bindingproteins. The GGGGCC repeat RNA also binds and sequesters RanGAP1 toimpair nucleocytoplasmic transport of RNA and proteins (Zhang et al.,Nature 525:56-61, 2015). Selectively targeting any of these repeatexpansion RNAs could add therapeutic benefit in these neurologicaldiseases.

The present invention contemplates a method of treating a disease ordisorder wherein aberrant RNAs themselves cause pathogenic effects,rather than acting through the agency of protein expression orregulation of protein expression. In some embodiments, the disease ordisorder is mediated by repeat RNA, such as those described above or inTables 1 and 2. In some embodiments, the disease or disorder is a repeatexpansion disease in which the repeat resides in the coding regions ofmRNA. In some embodiments, the disease or disorder is a repeat expansiondisease in which the repeat resides in the noncoding regions of mRNA. Insome embodiments, the disease or disorder is selected from Huntington'sdisease (HD), dentatorubral-pallidoluysian atrophy (DRPLA),spinal-bulbar muscular atrophy (SBMA), or a spinocerebellar ataxia (SCA)selected from SCA1, SCA2, SCA3, SCA6, SCAT, or SCA17. In someembodiments, the disease or disorder is selected from Fragile XSyndrome, myotonic dystrophy (DM1 or dystrophia myotonica), Friedreich'sAtaxia (FRDA), a spinocerebellar ataxia (SCA) selected from SCAB, SCA10,or SCA12, or C9FTD (amyotrophic lateral sclerosis or ALS).

In some embodiments, the disease is amyotrophic lateral sclerosis (ALS),Huntington's disease (HD), frontotemporal dementia (FTD), myotonicdystrophy (DM1 or dystrophia myotonica), or Fragile X Syndrome.

In some embodiments, the present invention provides a method of treatinga disease or disorder mediated by repeat RNA, comprising the step ofadministering to a patient in need thereof a compound of the presentinvention. Such compounds are described in detail herein.

Also provided is a method of producing a small molecule that modulatesthe activity of a target repeat expansion RNA to treat a disease ordisorder, comprising the steps of: screening one or more disclosedcompounds for binding to the target repeat expansion RNA; and analyzingthe results by an RNA binding assay disclosed herein. In someembodiments, the repeat expansion RNA causes a disease or disorderselected from HD, DRPLA, SBMA, SCA1, SCA2, SCA3, SCA6, SCAT, or SCA17.In some embodiments, the disease or disorder is selected from Fragile XSyndrome, DM1, FRDA, SCAB, SCA10, SCA12, or C9FTD.

Other Target RNAs and Diseases/Conditions

An association is known to exist between a large number of additionalRNAs and diseases or conditions, some of which are shown below in Table3. Accordingly, in some embodiments of the methods described above, thetarget RNA is selected from those in Table 3. In some embodiments, thedisease or disorder is selected from those in Table 3.

TABLE 3 Target RNAs and Associated Diseases/Conditions UP/DOWN GENECLASS REGULATED? TA INDICATION(S) MYC TF down Onco cancer STAT3 TF downOnco cancer C9orf72 TRED down Neuro ALS, FTD FOXP3 TF down I&I, I-Oimmuno-oncology; I&I MIR155 miRNA down Onco, I&I, ALS, fibrosis, cancerNeuro APOC3 apoprotein down Cardio chylomicronemia syndrome JUN TF downI&I I&I RSV genomic down Viral RSV KRAS TF down Onco cancer BCL2L1 IAPdown Onco cancer HIF1A TF down Onco cancer SMARCA2 helicase down Oncocancer SNCA down Neuro PD CCNE1 cyclin down Onco cancer FOXM1 TA downOnco cancer MYB TF down Onco cancer PTPN11 phosphatase down Onco, I&Icancer, SLE CD40LG TNF down I&I inflammation NFE2L2 TF up I&I multiplesclerosis RORC NHR down I&I I&I ZIKV genomic down Viral ZIKV DENVgenomic down Viral DENV AR NHR down Onco prostate cancer ASGR1 downCardio CVD BCL2 IAP down Onco cancer BDNF NF up Neuro Huntington'sDisease BRD4 epi down Onco cancer CD40 TNF down I&I immuno-oncology CD47Ig down I&I, I-O immuno-oncology CTLA4 Ig down I&I, I-O immuno-oncology;I&I CTNNB1 adhesion down Onco cancer DMPK TRED down Neuro Myotonicdystrophy type 1 (DM1) EIF4E IF down Onco cancer FOXA1 TA down Oncocancer GATA3 TF down Onco cancer IKZF1 TF down Onco cancer IKZF3 TF downOnco cancer IL17A IL down I&I inflammatory & autoimmune diseases IL23AIL down I&I inflammatory & autoimmune diseases IL6 IL down I&Irheumatoid arthritis ITGA1 integrin down I&I RA ITGA5 integrin down Oncosolid tumors ITGAE integrin down I&I UC, Crohns ITGB2, integrin down I&Ipsoriasis ITGAL ITGB7 integrin down I&I UC, Crohns MAPT cytoskeletondown Neuro Alzheimer's disease MAX TF down Onco cancer MDM2 E3 down Oncocancer MDM4 E3 down Onco cancer MIR21 miRNA down Onco cancer NR4A2 TFdown Neuro PD PTEN phosphatase up Onco cancer PTPN1 phosphatase downMetab Type 2 diabetes RUNX1 TF down Onco cancer SIRPA glycoprotein downI&I, I-O immuno-oncology SMAD7 TGF down I&I IBD SOX2 TF down Onco cancerSTAT5A TF down Onco cancer TERT telomerase down Onco cancer TGFB1 TGFdown Fibrosis fibrosis TNF TNF down I&I inflammatory disease TNFRSF11ATNF down osteoporosis TNFSF11 TNF down osteoporosis TWIST1 TF down Oncocancer WNT1 Onco cancer HepB down Viral HepB influenza down Viralinfluenza DGAT2 transferase down NASH DNMT3 DNMT down Onco cancer ERBB3pseudokinase down Onco cancer FBXW7 F-box (E3) down Onco cancer FMR1TRED down Neuro Fragile × Syndrome; FTXAS FOS TF down FXN TRED downNeuro Friedreich's Ataxia IRAK3 pseudokinase down I&I I&I MECP2 TFup/down Genetic Dz Rett Syndrome MIR17HG miRNA down Onco cancer NF1 downneurofibromatosis ORAI1 ion channel down I&I I&I PCSK9 convertase downCardio hypercholesterolemia PSMB8 protease down I&I I&I SKP2 F-box (E3)down Onco cancer USP1 protease down Onco cancer USP7 protease down Oncocancer HIF1A TF up I&I wound repair & regeneration HOTAIR IncRNA downOnco cancer IKBKG down I&I I&I IKK2 kinase down I&I I&I MALAT1 IncRNAdown Onco cancer PRMT5 KMT down Onco cancer BCL6 IAP down Onco cancerGRN down Neuro neurological diseases ABCA1 transporter Cardio coronaryartery disease ABCB11 transporter Primary Biliary Sclerosis ABCB4transporter Primary Biliary Sclerosis ABCG5 transporter Cardio coronaryartery disease ABCG8 transporter Cardio coronary artery disease ADIPOQhormone up Metab diabetes; obesity; metabolic syndrome APOA1 Cardiohypercholesterolemia APOA5 Cardio hypercholesterolemia ATPA2 Ca ATPaseup Genetic Dz congestive heart failure ATXN1 TRED Neuro spinocerebellarataxia 1 ATXN10 TRED down Neuro spinocerebellar ataxia 10 ATXN2 TREDNeuro spinocerebellar ataxia 2 ATXN3 TRED Neuro spinocerebellar ataxia 3ATXN7 TRED Neuro spinocerebellar ataxia 7 ATXN8 TRED Neurospinocerebellar ataxia 8 BACE1 protease down Neuro Alzheimer's diseaseBIRC2 IAP down Onco cancer BIRC3 IAP down Onco cancer BIRC5 IAP downOnco cancer BRCA1 DNA repair up Onco cancer CACNA1A ion channel Neuroepisodic ataxia type 2 CD247 TCR I&I I&I CD274 down I-O immuno-oncologyCETP transfer down cardiovascular CFH complement macular degenerationCFTR ion channel up Genetic Dz Cystic Fibrosis CNBP TRED down NeuroMyotonic dystrophy type 2 (DM2) CNTF NF macular degeneration DIO2deiodinase Metab dyslipidemia DMD cytoskeleton Neuro Duchenne MuscularDystrophy; Becker's MD F7 protease up Hematology hemophilia F8 proteaseup Hematology hemophilia F9 protease up Hematology hemophilia FGF3 downGenetic Dz achondroplasia HAMP down Genetic Dz thalassemia; hereditaryhemochromatosis HAVCR2 down I&I, I-O inflammatory diseases; immuno-oncology HBG1, hemoglobin up Hematology sickle cell anemia; beta- HBG2thalassemia HIF1AN Onco cancer IDH1 dehydrogenase down Onco cancer IL1IL down I&I rheumatoid arthritis IRAK4 kinase down I&I I&I IRF5 TF I-Oimmuno-oncology LAMA1 ECM Genetic Dz Merosin-deficient congenital MD(MDCA1) LARGE1 Genetic Dz Muscular Dystroglycanopathy Type B, 6 LINGO1down Neuro neurodegeneration MBNL1 splice factor Neuro MyotonicDystrophy MCL1 IAP down Onco cancer MERTK kinase I&I Lupus METAP2peptidase down Onco, I&I cancer, obesity, autoimmune MTOR kinase Oncocancer NANOG TF Neuro neurological diseases NF2 neurofibromatosis NSD-3KMT down Onco cancer PAH hydroxylase Genetic Dz phenylketonuria PCSK6convertase up Cardio hypertension PDCD1 I-O immuno-oncology PDK1, kinasepolycystic kidney disease PDK2 PDX1 TF Metab diabetes PPARGC1A PPARNeuro Neurological diseases; obesity PRKAA1 kinase Metab diabetes PRKAB1kinase Metab diabetes PRKAG1 kinase Metab diabetes RTN4 down Neuroneurodegeneration RTN4R down Neuro neurodegeneration SCARB1 HDL Cardiocoronary artery disease receptor SIRT6 KDAC down Onco cancer SMN2 upNeuro Spinal Muscular Atrophy SMURF2 down SORT1 glycoprotein Cardiocoronary artery disease SSPN cytoskeleton Genetic Dz Duchenne's MD TBX21I-O immuno-oncology THRB NHR dyslipidemia; NASH; NAFLD TNFAIP3 I&Iinflammatory dz; liver failure; liver transplant TRIB1 pseudokinaseCardio coronary artery disease TTR down Genetic Dz amyloidosis UTRNcytoskeleton Genetic Dz Duchenne Muscular Dystrophy XIAP IAP down Oncocancer RAGE ANGPTL3

TABLE 4 Additional Target RNAs COMMON UP/DOWN GENE NAME CLASS REGULATED?TA INDICATION(S) CTSL cathepsin L protease up neuro PD AR AR-V7 NHR downcancer CRPC JMJD6 JMJD6 HDM down cancer GBM DNMT1 DNMT1 Me-transferasedown cancer GBM ASGR1 ASGR1 ASG receptor down CVD CVD NAMPT NAMPTtransferase down cancer various IRE ARID1B ARID1B SOX10 SOX10 HNF1B TCF2PTPN2 PTPN2 NLGN3 NLGN3 ETS

2. Compounds and Uses Thereof

It has now been found that compounds of this invention, andpharmaceutically acceptable compositions thereof, are effective asagents for use in drug discovery and for preparing nucleic acidconjugates that are useful in drug discovery. For example, compounds ofthe present invention, and pharmaceutical compositions thereof, areuseful in determining the location and/or structure of an active site orallosteric sites and/or the tertiary structure of a target RNA.

In one aspect, disclosed compounds are useful as diagnostic or assayreagents. In some embodiments, the present invention provides a methodof determining the three-dimentional structure, binding site of a ligandof interest, or accessibility of a nucleotide in a target nucleic acid,comprising: contacting the target nucleic acid with a disclosedcompound; irradiating the compound; determining whether covalentmodification of a nucleotide of the nucleic acid has occurred; andoptionally deriving the pattern of nucleotide modification, thethree-dimentional structure, ligand binding site, or other structuralinformation about the nucleic acid.

In another aspect, the present invention provides a method of preparinga nucleic acid conjugate, comprising: contacting a target nucleic acidwith a disclosed compound; irradiating the compound; and optionallyisolating the resulting nucleic acid conjugate by an affinity assay,pull-down method, or other means known in the art. Such nucleic acidconjugates are useful for determining structural information about thetarget nucleic acid comprised in the conjugate that allows one ofordinary skill to design small molecule drugs that bind to the targetnucleic acid in vivo to treat a disease, disorder, or condition, such asthose disclosed herein. In some embodiments, the nucleic acid is a RNA,such as a disease-causing RNA as described herein.

In another aspect, the present invention provides a method of assessingselectivity across a transcriptome for a drug candidate, comprisingcontacting a biological sample comprising two or more RNA transcriptswith a drug candidate comprising a disclosed photoactivatable grouptethered to the drug candidate; irradiating the drug candidate; anddetermining covalent modification of an RNA transcript.

In another aspect, the present invention provides a method ofdetermining target occupancy in cells of a drug candidate, comprisingcontacting a biological sample comprising a target RNA with a disclosedcompound or drug candidate comprising a disclosed photoactivatable grouptethered to the drug candidate; irradiating the compound or drugcandidate; and determining covalent modification of the target RNA. Insome embodiments, the method confirms target engagement and correlatesbinding with cellular biology.

In some embodiments, the method enables assembling a binding site map byidentifying subsite binding to explicate the biochemical mode of action.

In some embodiments, the method further enables relating targetengagement to target mutations and cell function. This is useful forunderstanding the molecular mechanism of drug candidates in cells.

In another aspect, the present invention provides a method ofdetermining the presence of a RNA binding protein (RBP) that isassociated with a target RNA comprising: contacting the target RNA witha disclosed compound; irradiating the compound; and determining whethercovalent modification of an amino acid of the RBP has occurred.

In some embodiments, the present invention provides a compoundcomprising:

-   -   (a) a small molecule ligand that binds selectively to one or        more binding sites on a target RNA;    -   (b) a photoactivatable group (or “warhead”) that is covalently        conjugated to the small molecule ligand and that forms a        covalent bond to the target RNA upon irradiation with visible        light or ultraviolet light;    -   (c) optionally, a click-ready group;    -   (d) optionally, a pull-down group; and    -   (e) optionally, one or two tethering groups that covalently link        the small molecule ligand and the photoactivatable group and,        optionally, the click-ready group.

Without wishing to be bound by any particular theory, it is believedthat compounds of the present invention bind selectively to one or moreactive or allosteric sites on a target RNA, or other sites determined bybinding interactions between the small molecule ligand and the structureof the target RNA; upon irradiation, covalently modify one or morepositions of the target RNA, such as a C8 carbon of an adenosine orguanosine nucleotide or a 2′—OH group of the target RNA; and maysubsequently be used to identify the active site or other binding sitesby sequencing or other analysis of the distribution of modifiednucleotides because the pattern of modification will be constrained bythe length and conformation of the tether that connects the ligand withthe RNA warhead. The target RNA may be inside a cell, in a cell lysate,or in isolated form prior to contacting the compound. Screening oflibraries of disclosed compounds will identify highly potentsmall-molecule modulators of the activity of the target RNA. It isunderstood that such small molecules identified by such screening may beused as modulators of a target RNA to treat, prevent, or ameliorate adisease or condition in a patient in need thereof

In one aspect, the present invention provides a compound of the generalFormula I:

or a pharmaceutically acceptable salt thereof; wherein:

-   Ligand is a small molecule RNA binder;-   T¹ is a bivalent tethering group; and-   R^(mod) is a photoactivatable group; wherein each variable is as    defined below.

In another aspect, the present invention provides a compound of thegeneral Formula II:

or a pharmaceutically acceptable salt thereof; wherein:

-   Ligand is a small molecule RNA binder;-   T¹ is a bivalent tethering group;-   T² is a covalent bond or a bivalent tethering group;-   R^(mod) is a photoactivatable group; and-   R^(CG) is a click-ready group or a pull-down group.

In another aspect, the present invention provides a compound of thegeneral Formula III:

or a pharmaceutically acceptable salt thereof; wherein:

-   Ligand is a small molecule RNA binder;-   T¹ is a trivalent tethering group;-   T² is a bivalent tethering group;-   R^(mod) is a photoactivatable group; and-   R^(CG) is a click-ready group or a pull-down group; wherein each    variable is as defined below.

In another aspect, the present invention provides a compound of thegeneral formula II-a:

or a pharmaceutically acceptable salt thereof; wherein:

-   Ligand is a small molecule RNA binder;-   T¹ is a covalent bond or a bivalent tethering group;-   T² is a covalent bond or a bivalent tethering group;-   R^(mod) is a photoactivatable group; and-   R^(CG) is a click-ready group or a pull-down group; wherein each    variable is as defined below.

In another aspect, the present invention provides a compound of thegeneral formulae II-b or II-c:

or a pharmaceutically acceptable salt thereof; wherein:

-   Ligand is a small molecule RNA binder;-   T¹ is a bivalent tethering group;-   R^(mod) is a photoactivatable group; and-   R^(CG) is a click-ready group or a pull-down group; wherein each    variable is as defined below.

In another aspect, the present invention provides a RNA conjugatecomprising a target RNA and a compound of any of Formulae I, II, II-a,or III, wherein R^(mod) forms a covalent bond to the target RNA afterirradiation with visible light or ultraviolet light.

In some embodiments, the present invention provides a RNA conjugate ofFormula IV:

wherein Ligand is a small molecule that binds to a target RNA;

-   RNA represents the target RNA;-   T¹ is a bivalent tethering group; and-   R^(mod) is a photoactivatable group;-   wherein each variable is as defined below.

In some embodiments, the present invention provides a RNA conjugate ofFormula V:

wherein Ligand is a small molecule that binds to a target RNA;

-   RNA represents the target RNA;-   T¹ is a trivalent tethering group;-   T² is a bivalent tethering group;-   R^(mod) is a photoactivatable group; and-   R^(CG) is a click-ready group or a pull-down group;-   wherein each variable is as defined below.

In some embodiments, the present invention provides a RNA conjugate ofFormula VI:

wherein Ligand is a small molecule that binds to a target RNA;

-   RNA represents the target RNA;-   T¹ is a bivalent tethering group;-   T² is a covalent bond or a bivalent tethering group;-   R^(mod) is a photoactivatable group; and-   R^(CG) is a click-ready group or a pull-down group;-   wherein each variable is as defined below.

In some embodiments, the present invention provides a RNA conjugate ofFormula VI-a:

wherein Ligand is a small molecule that binds to a target RNA;

-   RNA represents the target RNA;-   T¹ is a bivalent tethering group;-   T² is a covalent bond or a bivalent tethering group;-   R^(mod) is a photoactivatable group; and-   R^(CG) is a click-ready group or a pull-down group;-   wherein each variable is as defined below.

In another aspect, the present invention provides a conjugate comprisinga target RNA, a compound of Formulae II or III, and a pull-down group,wherein R^(mod) forms a covalent bond to the target RNA.

In some embodiments, the present invention provides a RNA conjugate ofFormula VII:

wherein Ligand is a small molecule that binds to a target RNA;

-   RNA represents the target RNA;-   T¹ is a trivalent tethering group;-   T² is a bivalent tethering group;-   R^(mod) is a photoactivatable group;-   R^(CP) is a reaction product resulting from a click reaction between    a click-ready group and an appropriate functional group on R^(PD);    and-   R^(PD) is a pull-down group;-   wherein each variable is as defined below. In some embodiments,    R^(CP) is

In some embodiments, the present invention provides a RNA conjugate ofFormula VIII:

wherein Ligand is a small molecule that binds to a target RNA;

-   RNA represents the target RNA;-   T¹ is a bivalent tethering group;-   T² is a covalent bond or a bivalent tethering group;-   R^(mod) is a photoactivatable group;-   R^(CP) is a reaction product resulting from a click reaction between    a click-ready group and an appropriate functional group on R^(PD);    and-   R^(PD) is a pull-down group;-   wherein each variable is as defined below. In some embodiments,    R^(CP) is

In some embodiments, the present invention provides a RNA conjugate ofFormula VIII-a:

wherein Ligand is a small molecule that binds to a target RNA;

-   RNA represents the target RNA;-   T¹ is a bivalent tethering group;-   T² is a covalent bond or a bivalent tethering group;-   R^(mod) is a photoactivatable group;-   R^(CP) is a reaction product resulting from a click reaction between    a click-ready group and an appropriate functional group on R^(PD);    and-   R^(PD) is a pull-down group;-   wherein each variable is as defined below. In some embodiments,    R^(CP) is

In one aspect, the present invention provides a compound of Formula X-a:

or a tautomer or pharmaceutically acceptable salt thereof, wherein:

-   Ar¹ is an optionally substituted phenyl or optionally substituted    5-6 membered monocyclic heteroaromatic ring having 1-4 heteroatoms    independently selected from nitrogen, oxygen, or sulfur;-   Ar² is an optionally substituted 5-6 membered monocyclic    heteroaromatic ring having 1-4 heteroatoms independently selected    from nitrogen, oxygen, or sulfur, or an optionally substituted 8-10    membered bicyclic heteroaromatic ring having 1-5 heteroatoms    independently selected from nitrogen, oxygen, or sulfur;-   X is selected from a bivalent C₁₋₃ alkylene chain wherein 1-2    methylene units of the chain are independently and optionally    replaced with —O—, —NR⁶—, —S—, —C(O)—, —CO₂—, —CS—, —C(NR⁶)—,    —S(O)—, or —S(O)₂—;-   R¹ is selected from —C(O)R⁶, —CO₂R, —C(O)NR₂, —C₁₋₆ aliphatic, —CN,    —(CH₂)₁₋₃OR, —(CH₂)₁₋₃NHR, —N(R)C(O)OR⁶, —N(R⁶)C(O)R, —OC(O)R, —OR,    —NHR⁶, or —N(R)C(O)NHR;-   R² is a photoactivatable group that optionally comprises a    click-ready group if R³ is absent;-   R³ is absent or is a click-ready group or a pull-down group; each R⁶    is independently hydrogen or C₁₋₆ alkyl optionally substituted with    1, 2, 3, 4, 5, or 6 deuterium or halogen atoms;-   each R is independently hydrogen or an optionally substituted group    selected from C₁₋₆ aliphatic, a 3-8 membered saturated or partially    unsaturated monocyclic carbocyclic ring, phenyl, an 8-10 membered    bicyclic aromatic carbocyclic ring, a 4-8 membered saturated or    partially unsaturated monocyclic heterocyclic ring having 1-2    heteroatoms independently selected from nitrogen, oxygen, or sulfur,    a 5-6 membered monocyclic heteroaromatic ring having 1-4 heteroatoms    independently selected from nitrogen, oxygen, or sulfur, or an 8-10    membered bicyclic heteroaromatic ring having 1-5 heteroatoms    independently selected from nitrogen, oxygen, or sulfur;-   L¹ is a C₁₋₂₀ bivalent, trivalent, or tetravalent straight or    branched hydrocarbon chain wherein 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10    methylene units of the chain are independently and optionally    replaced with a natural or non-natural amino acid, —O—, —C(O)—,    —C(O)O—, —OC(O)—, —N(R)—, —C(O)N(R)—, —(R)NC(O)—, —OC(O)N(R)—,    —(R)NC(O)O—, —N(R)C(O)N(R)—, —S—, —SO—, —SO₂N(R)—, —(R)NSO₂—,    —C(S)—, —C(S)O—, —OC(S)—, —C(S)N(R)—, —(R)NC(S)—, —(R)NC(S)N(R)—, or    —Cy—; and 1-20 of the methylene units of the chain are independently    and optionally replaced with —OCH₂CH₂—;-   each -Cy- is independently a bivalent optionally substituted 3-8    membered saturated or partially unsaturated monocyclic carbocyclic    ring, optionally substituted phenylene, an optionally substituted    4-8 membered saturated or partially unsaturated monocyclic    heterocyclic ring having 1-3 heteroatoms independently selected from    nitrogen, oxygen, or sulfur, an optionally substituted 5-6 membered    monocyclic heteroaromatic ring having 1-4 heteroatoms independently    selected from nitrogen, oxygen, or sulfur, an optionally substituted    8-10 membered bicyclic or bridged bicyclic saturated or partially    unsaturated heterocyclic ring having 1-5 heteroatoms independently    selected from nitrogen, oxygen, or sulfur, or an optionally    substituted 8-10 membered bicyclic or bridged bicyclic    heteroaromatic ring having 1-5 heteroatoms independently selected    from nitrogen, oxygen, or sulfur; and-   n is 0 or 1.

In another aspect, the present invention provides a compound of FormulaX-b:

or a tautomer or pharmaceutically acceptable salt thereof, wherein:

-   Ar¹ is an optionally substituted phenyl or optionally substituted    5-6 membered monocyclic heteroaromatic ring having 1-4 heteroatoms    independently selected from nitrogen, oxygen, or sulfur;-   Ar² is an optionally substituted 5-6 membered monocyclic    heteroaromatic ring having 1-4 heteroatoms independently selected    from nitrogen, oxygen, or sulfur, or an optionally substituted 8-10    membered bicyclic heteroaromatic ring having 1-5 heteroatoms    independently selected from nitrogen, oxygen, or sulfur;-   wherein one of Ar¹ or Ar² is substituted with one R²;-   X is selected from a bivalent C₁₋₃ alkylene chain wherein 1-2    methylene units of the chain are independently and optionally    replaced with —O—, —NR⁶—, —S—, —C(O)—, —CO₂——CS—, —C(NR⁶)—, —S(O)—,    or —S(O)₂—;-   R¹ is selected from —C(O)R⁶, —CO₂R, —C(O)NR₂, —C₁₋₆ aliphatic, —CN,    —(CH₂)₁₋₃OR, —(CH₂)₁₋₃NHR, —N(R)C(O)OR⁶, —N(R⁶)C(O)R, —OC(O)R, —OR,    —NHR⁶, or —N(R)C(O)NHR;-   R² is a photoactivatable group that optionally comprises a    click-ready group if R³ is absent;-   R³ is absent or is a click-ready group or a pull-down group;-   each R⁶ is independently hydrogen or C₁₋₆ alkyl optionally    substituted with 1, 2, 3, 4, 5, or 6 deuterium or halogen atoms;-   each R is independently hydrogen or an optionally substituted group    selected from C₁₋₆ aliphatic, a 3-8 membered saturated or partially    unsaturated monocyclic carbocyclic ring, phenyl, an 8-10 membered    bicyclic aromatic carbocyclic ring, a 4-8 membered saturated or    partially unsaturated monocyclic heterocyclic ring having 1-2    heteroatoms independently selected from nitrogen, oxygen, or sulfur,    a 5-6 membered monocyclic heteroaromatic ring having 1-4 heteroatoms    independently selected from nitrogen, oxygen, or sulfur, or an 8-10    membered bicyclic heteroaromatic ring having 1-5 heteroatoms    independently selected from nitrogen, oxygen, or sulfur;-   L¹ is a C₁₋₂₀ bivalent or trivalent straight or branched hydrocarbon    chain wherein 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 methylene units of    the chain are independently and optionally replaced with a natural    or non-natural amino acid, —O—, —C(O)—, —C(O)O—, —OC(O)—, —N(R)—,    —C(O)N(R)—, —(R)NC(O)—, —OC(O)N(R)—, —(R)NC(O)O—, —N(R)C(O)N(R)—,    —S—, —SO—, —SO₂—, —SO₂N(R)—, —(R)NSO₂—, —C(S)—, —C(S)O—, —OC(S)—,    —C(S)N(R)—, —(R)NC(S)—, —(R)NC(S)N(R)—, or -Cy-; and 1-20 of the    methylene units of the chain are independently and optionally    replaced with —OCH₂CH₂—;-   each -Cy- is independently a bivalent optionally substituted 3-8    membered saturated or partially unsaturated monocyclic carbocyclic    ring, optionally substituted phenylene, an optionally substituted    4-8 membered saturated or partially unsaturated monocyclic    heterocyclic ring having 1-3 heteroatoms independently selected from    nitrogen, oxygen, or sulfur, an optionally substituted 5-6 membered    monocyclic heteroaromatic ring having 1-4 heteroatoms independently    selected from nitrogen, oxygen, or sulfur, an optionally substituted    8-10 membered bicyclic or bridged bicyclic saturated or partially    unsaturated heterocyclic ring having 1-5 heteroatoms independently    selected from nitrogen, oxygen, or sulfur, or an optionally    substituted 8-10 membered bicyclic or bridged bicyclic    heteroaromatic ring having 1-5 heteroatoms independently selected    from nitrogen, oxygen, or sulfur; and-   n is 0 or 1.

As defined generally above, Ar¹ is an optionally substituted phenyl oroptionally substituted 5-6 membered monocyclic heteroaromatic ringhaving 1-4 heteroatoms independently selected from nitrogen, oxygen, orsulfur.

In some embodiments, Ar¹ is an optionally substituted phenyl. In someembodiments, Ar¹ is an optionally substituted 5-6 membered monocyclicheteroaromatic ring having 1-4 heteroatoms independently selected fromnitrogen, oxygen, or sulfur.

In some embodiments, Ar¹ is phenyl optionally subsituted with 1, 2, 3,or 4 substituents selected from halogen, —-C₁₋₆ aliphatic, —CN, —OR,—NR₂, —CO₂R, —C(O)R, —SR, or —C(O)NR₂. In some embodiments, the optionalsubstituents are selected from halogen, —CN, —C₁₋₆ alkyl, or —OMe. Insome embodiments, the optional substituents are halogen. In someembodiments, 1 or 2 substituents are present. In some embodiments, Ar¹is selected from those depicted in Table 5, below.

As defined generally above, Ar² is an optionally substituted 5-6membered monocyclic heteroaromatic ring having 1-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur, or anoptionally substituted 8-10 membered bicyclic heteroaromatic ring having1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

In some embodiments, Ar² is an optionally substituted 5-6 memberedmonocyclic heteroaromatic ring having 1-4 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur. In some embodiments, Ar² isan optionally substituted 8-10 membered bicyclic heteroaromatic ringhaving 1-5 heteroatoms independently selected from nitrogen, oxygen, orsulfur.

In some embodiments, Ar² is an optionally substituted pyridinyl,pyrimidinyl, imidazolyl, or pyrrolyl. In some embodiments, Ar² is anoptionally substituted pyridinyl. In some embodiments, Ar² is pyridinyl.In some embodiments, Ar² is 3- or 4-pyridinyl. In some embodiments, Ar²is selected from those depicted in Table 5, below.

As defined generally above, X is a bivalent C₁₋₃ alkylene chain wherein1-2 methylene units of the chain are independently and optionallyreplaced with —O—, —S—, —C(O)—, —CO₂——CS—, —C(NR⁶)—, —S(O)—, or —S(O)₂—.

In some embodiments, X is —CH₂—, —O—, —NR⁶—, —S—, —C(O)—, —CO₂——CS—,—C(NR⁶)—, —S(O)—, or —S(O)₂—. In some embodiments, X is a C₂ alkylenechain wherein 1-2 methylene units of the chain are independently andoptionally replaced with —O—, —NR⁶—, —S—, —C(O)—, —CO₂——CS—, —C(NR⁶)—,—S(O)—, or —S(O)₂—. In some embodiments, X is a C₃ alkylene chainwherein 1-2 methylene units of the chain are independently andoptionally replaced with —O—, —NR⁶—, —S—, —C(O)—, —CO₂——CS—, —C(NR⁶)—,—S(O)—, or —S(O)₂—.

In some embodiments, X is selected from —CH₂O—, CH₂C(O)—, —C(O)CH₂—,—CH₂C(O)O—, —C(O)CH₂O—, —C(O)O—, —C(O)N(R⁶)—, —CH₂N(R⁶)—, or—N(R⁶)C(O)—. In some embodiments, X is —OCH₂—or —CH₂O-. In someembodiments, X is selected from those depicted in Table 5, below.

As defined generally above, R¹ is selected from —C(O)R⁶, —CO₂R,—C(O)NR₂, —C₁₋₆ aliphatic, —CN, —(CH₂)₁₋₃OR, —(CH₂)₁₋₃NHR, —N(R)C(O)OR⁶,—N(R⁶)C(O)R, —OC(O)R, —OR, —NHR⁶, or —N(R)C(O)NHR.

In some embodiments, R¹ is —C(O)R⁶. In some embodiments, R¹ is —CO₂R. Insome embodiments, R¹ is —C(O)NR₂. In some embodiments, R¹ is —C₁₋₆aliphatic. In some embodiments, R¹ is —CN. In some embodiments, R¹ is—(CH₂)₁₋₃OR⁶. In some embodiments, R¹ is —(CH₂)₁₋₃NHR. In someembodiments, R¹ is —N(R)C(O)OR⁶. In some embodiments, R¹ is —N(R⁶)C(O)R.In some embodiments, R¹ is —OC(O)R. In some embodiments, R¹ is —OR. Insome embodiments, R¹ is —NHR⁶. In some embodiments, R¹ is —N(R)C(O)NHR.In some embodiments, le is selected from those depicted in Table 5,below.

As defined generally above, R² is a photoactivatable group thatoptionally comprises a click-ready group if R³ is absent. In someembodiments, R² is a photoactivatable group. In some embodiments, R² isa photoactivatable group further substituted with a click-ready group.

In some embodiments, R² is a functional group that generates a radical,an aryl or heteroaryl carbocation, a nitrene, or a carbene intermediateupon irradiation with ultraviolet (UV) radiation, and that is optionallysubstituted with a click-ready group or pull-down group if R³ is absent.In some embodiments, R² is an optionally substituted phenyl or 8-10membered bicyclic aromatic carbocyclic azide or 5-8 membered heteroarylor 8-10 membered bicyclic heteroaryl azide, optionally substitutedbenzoyl azide or 5-8 membered heteroaroyl azide or 8-10 memberedheteroaroyl azide wherein 1-3 atoms of the ring atoms are selected fromnitrogen, sulfur, or oxygen, optionally substituted phenyl or 8-10membered bicyclic aromatic carbocyclic diazonium salt, optionallysubstituted 5-8 membered heteroaryl or 8-10 membered bicyclic heteroaryldiazonium salt wherein 1-3 atoms of the ring atoms are selected fromnitrogen, sulfur, or oxygen, optionally substituted C₂₋₆ aliphatic diazofunctional group, optionally substituted C₂₋₆ aliphatic diazirine, oroptionally substituted diphenyl or 8-10-membered diheteroaryl ketonewherein 1-3 atoms of the ring atoms are selected from nitrogen, sulfur,or oxygen, optionally substituted dihydropyrene, optionally substitutedspirooxazine, optionally substituted anthracene, optionally substitutedfulgide, optionally substituted spiropyran, optionally substituteda-pyrone or optionally substituted pyrimidone; and which is optionallysubstituted with a click-ready group or pull-down group. In someembodiments, the click-ready group is a C₁₋₆ alkyl azide or alkyne. Insome embodiments, R² is selected from

wherein Y⁻ is a pharmaceutically acceptable anion.

In some embodiments, R² is selected from those depicted in Table 5,below.

As defined generally above, R³ is absent or is a click-ready group or apull-down group. In some embodiments, R³ is absent. In some embodiments,R³ is a click-ready group. In some embodiments, R³ is a pull-down group.In some embodiments, R³ is a C₁₋₆ alkyl azide, C₁₋₆ alkyne, or biotin.

In some embodiments, R³ is selected from those depicted in Table 5,below.

As defined generally above, each R⁶ is independently hydrogen or C₁₋₆alkyl optionally substituted with 1, 2, 3, 4, 5, or 6 deuterium orhalogen atoms.

In some embodiments, R⁶ is hydrogen. In some embodiments, R⁶ is C₁₋₆alkyl optionally substituted with 1, 2, 3, 4, 5, or 6 deuterium orhalogen atoms.

In some embodiments, R⁶ is C₁₋₃ alkyl optionally substituted with 1, 2,or 3 halogen atoms.

In some embodiments, R⁶ is selected from those depicted in Table 5,below.

As defined generally above, L¹ is a C₁₋₂₀ bivalent or trivalent straightor branched hydrocarbon chain wherein 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10methylene units of the chain are independently and optionally replacedwith a natural or non-natural amino acid, —O—, —C(O)—, —C(O)O—, —OC(O)—,—N(R)—, —C(O)N(R)—, —(R)NC(O)—, —OC(O)N(R)—, —(R)NC(O)O—,—N(R)C(O)N(R)—, —S—, —SO—, —SO₂—, —SO₂N(R)—, —(R)NSO₂—, —C(S)—, —C(S)O—,—OC(S)—, —C(S)N(R)—, —(R)NC(S)—, —(R)NC(S)N(R)—, or -Cy-; and 1-20 ofthe methylene units of the chain are independently and optionallyreplaced with —OCH₂CH₂—.

In some embodiments, L¹ is a C₁₋₁₀ bivalent or trivalent straight orbranched hydrocarbon chain wherein 1, 2, 3, 4, or 5 methylene units ofthe chain are independently and optionally replaced with a natural ornon-natural amino acid, —O—, —C(O)—, —C(O)O—, —OC(O)—, —N(R)—,—C(O)N(R)—, —(R)NC(O)—, —OC(O)N(R)—, —(R)NC(O)O—, —N(R)C(O)N(R)—, —S—,—SO—, —SO₂—, —SO₂N(R)—, —(R)NSO₂—, —C(S)—, —C(S)O—, —OC(S)—, —C(S)N(R)—,—(R)NC(S)—, —(R)NC(S)N(R)—, or -Cy-; and 1-5 of the methylene units ofthe chain are independently and optionally replaced with —OCH₂CH₂—. Insome embodiments, L¹ comprises 1-3 natural amino acids. In someembodiments, the amino acids are selected from proline, lysine, glycine,or alanine. In some embodiments, L¹ comprises 1-2-Cy- groups selectedfrom 1,2,3-triazolylene or 1,2,4-triazolylene. In some embodiments, L¹comprises 1-10, 1-8, 1-6, 1-4, 1-3, 1-2, 1, 2, or 3 —OCH₂CH₂—units.

In some embodiments, L¹ is selected from those depicted in Table 5,below.

As defined generally above, each -Cy- is independently a bivalentoptionally substituted 3-8 membered saturated or partially unsaturatedmonocyclic carbocyclic ring, optionally substituted phenylene, anoptionally substituted 4-8 membered saturated or partially unsaturatedmonocyclic heterocyclic ring having 1-3 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur, an optionally substituted 5-6membered monocyclic heteroaromatic ring having 1-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur, an optionallysubstituted 8-10 membered bicyclic or bridged bicyclic saturated orpartially unsaturated heterocyclic ring having 1-5 heteroatomsindependently selected from nitrogen, oxygen, or sulfur, or anoptionally substituted 8-10 membered bicyclic or bridged bicyclicheteroaromatic ring having 1-5 heteroatoms independently selected fromnitrogen, oxygen, or sulfur.

In some embodiments, -Cy- is a bivalent optionally substituted 3-8membered saturated or partially unsaturated monocyclic carbocyclic ring.In some embodiments, -Cy- is an optionally substituted phenylene. Insome embodiments, -Cy- is an optionally substituted 4-8 memberedsaturated or partially unsaturated monocyclic heterocyclic ring having1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur.In some embodiments, -Cy- is an optionally substituted 5-6 memberedmonocyclic heteroaromatic ring having 1-4 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur. In some embodiments, -Cy- isan optionally substituted 8-10 membered bicyclic or bridged bicyclicsaturated or partially unsaturated heterocyclic ring having 1-5heteroatoms independently selected from nitrogen, oxygen, or sulfur. Insome embodiments, -Cy- is an optionally substituted 8-10 memberedbicyclic or bridged bicyclic heteroaromatic ring having 1-5 heteroatomsindependently selected from nitrogen, oxygen, or sulfur.

In some embodiments, -Cy- is phenylene, pyridinylene, pyrimidinylene,1,2,3-triazolylene, or 1,2,4-triazolylene.

In some embodiments, -Cy- is selected from those depicted in Table 5,below.

As defined generally above, n is 0 or 1.

In some embodiments, n is 0. In some embodiments, n is 1.

In another aspect, the present invention provides a compound of FormulaXXV:

or a pharmaceutically acceptable salt thereof, wherein:

-   A¹ is an optionally substituted phenyl or optionally substituted 5-6    membered monocyclic heteroaromatic ring having 1-4 heteroatoms    independently selected from nitrogen, oxygen, or sulfur;-   Ar³ is an optionally substituted phenyl, an optionally substituted    5-6 membered monocyclic heteroaromatic ring having 1-4 heteroatoms    independently selected from nitrogen, oxygen, or sulfur, an    optionally substituted 8-12 membered bicyclic aromatic ring, or an    optionally substituted 8-10 membered bicyclic heteroaromatic ring    having 1-5 heteroatoms independently selected from nitrogen, oxygen,    or sulfur;-   X is selected from a bivalent C₁₋₃ alkylene chain wherein 1-2    methylene units of the chain are independently and optionally    replaced with —O—, —NR⁶—, —S—, —C(O)—, —CO₂——CS—, —C(NR⁶)—, —S(O)—,    or —S(O)₂—;-   X² is is selected from a bivalent C₁₋₃ alkylene chain wherein 1-2    methylene units of the chain are independently and optionally    replaced with —O—, —NR⁶—, —S—, —C(O)—, —CO₂——CS—, —C(NR⁶)—, —S(O)—,    or —S(O)₂—;-   R² is a photoactivatable group that optionally comprises a    click-ready group if R³ is absent;-   R³ is absent or is a click-ready group or a pull-down group;-   each R⁴ is independently R, halogen, —CN, —NO₂, —OR, —SR, —NR₂,    —S(O)₂R, —S(O)₂NR₂, —S(O)R, —C(O)R, —C(O)OR, —C(O)NR₂, —C(O)N(R)OR,    —OC(O)R, —OC(O)NR₂, —N(R)C(O)OR, —N(R)C(O)R, —N(R)C(O)NR₂,    —N(R)S(O)₂R, or —N(R)S(O)₂NR₂; or two instances of R⁴ may be taken    together with the atoms to which they are attached to form a C₄₋₈    partially unsaturated carbocyclic ring;-   each R⁵ is independently R, halogen, —CN, —NO₂, —OR, —SR, —NR₂,    —S(O)₂R, —S(O)₂NR₂, —S(O)R, —C(O)R, —C(O)OR, —C(O)NR₂, —C(O)N(R)OR,    —OC(O)R, —OC(O)NR₂, —N(R)C(O)OR, —N(R)C(O)R, —N(R)C(O)NR₂,    —N(R)S(O)₂R, or —N(R)S(O)₂NR₂; or two instances of R⁵ may be taken    together to form ═O or ═S;-   each R⁶ is independently hydrogen or C₁₋₆ alkyl optionally    substituted with 1, 2, 3, 4, 5, or 6 deuterium or halogen atoms;-   each R is independently hydrogen or an optionally substituted group    selected from C₁₋₆ aliphatic, a 3-8 membered saturated or partially    unsaturated monocyclic carbocyclic ring, phenyl, an 8-10 membered    bicyclic aromatic carbocyclic ring, a 4-8 membered saturated or    partially unsaturated monocyclic heterocyclic ring having 1-2    heteroatoms independently selected from nitrogen, oxygen, or sulfur,    a 5-6 membered monocyclic heteroaromatic ring having 1-4 heteroatoms    independently selected from nitrogen, oxygen, or sulfur, or an 8-10    membered bicyclic heteroaromatic ring having 1-5 heteroatoms    independently selected from nitrogen, oxygen, or sulfur;-   L² is a C₁₋₂₀ bivalent or trivalent, straight or branched,    optionally substituted hydrocarbon chain wherein 1, 2, 3, 4, 5, 6,    7, 8, 9, or 10 methylene units of the chain are independently and    optionally replaced with a natural or non-natural amino acid, —O—,    —C(O)—, —C(O)O—, —OC(O)—, —N(R)—, —C(O)N(R)—, —(R)NC(O)—,    —OC(O)N(R)—, —(R)NC(O)O—, —N(R)C(O)N(R)—, —S—, —SO—, —SO₂—,    —SO₂N(R)—, —(R)NSO₂—, —C(S)—, —C(S)O—, —OC(S)—, —C(S)N(R)—,    —(R)NC(S)—, —(R)NC(S)N(R)—, or -Cy-; and 1-20 of the methylene units    of the chain are independently and optionally replaced with    —OCH₂CH₂—;-   each -Cy- is independently a bivalent optionally substituted 3-8    membered saturated or partially unsaturated monocyclic carbocyclic    ring, optionally substituted phenylene, an optionally substituted    4-8 membered saturated or partially unsaturated monocyclic    heterocyclic ring having 1-3 heteroatoms independently selected from    nitrogen, oxygen, or sulfur, an optionally substituted 5-6 membered    monocyclic heteroaromatic ring having 1-4 heteroatoms independently    selected from nitrogen, oxygen, or sulfur, an optionally substituted    8-10 membered bicyclic or bridged bicyclic saturated or partially    unsaturated heterocyclic ring having 1-5 heteroatoms independently    selected from nitrogen, oxygen, or sulfur, or an optionally    substituted 8-10 membered bicyclic or bridged bicyclic    heteroaromatic ring having 1-5 heteroatoms independently selected    from nitrogen, oxygen, or sulfur;-   m is 0, 1, 2, 3, or 4; and-   p is 0, 1, 2, 3, or 4.

In another aspect, the present invention provides a compound of FormulaXXVI:

or a pharmaceutically acceptable salt thereof, wherein:

-   Ar¹ is an optionally substituted phenyl or optionally substituted    5-6 membered monocyclic heteroaromatic ring having 1-4 heteroatoms    independently selected from nitrogen, oxygen, or sulfur;-   Ar³ is an optionally substituted phenyl, an optionally substituted    5-6 membered monocyclic heteroaromatic ring having 1-4 heteroatoms    independently selected from nitrogen, oxygen, or sulfur, an    optionally substituted 8-12 membered bicyclic aromatic ring, or an    optionally substituted 8-10 membered bicyclic heteroaromatic ring    having 1-5 heteroatoms independently selected from nitrogen, oxygen,    or sulfur;-   X is selected from a bivalent C₁₋₃ alkylene chain wherein 1-2    methylene units of the chain are independently and optionally    replaced with —O—, —NR⁶—, —S—, —C(O)—, —CO₂——CS—, —C(NR⁶)—, —S(O)—,    or —S(O)₂—;-   X² is is selected from a bivalent C₁₋₃ alkylene chain wherein 1-2    methylene units of the chain are independently and optionally    replaced with —O—, —NR⁶—, —S—, —C(O)—, —CO₂——CS—, —C(NR⁶)—, —S(O)—,    or —S(O)₂—;-   R² is a photoactivatable group that optionally comprises a    click-ready group if R³ is absent; R³ is absent or is a click-ready    group or a pull-down group;-   each R⁴ is independently R, halogen, —CN, —NO₂, —OR, —SR, —NR₂,    —S(O)₂R, —S(O)₂NR₂, —S(O)R, —C(O)R, —C(O)OR, —C(O)NR₂, —C(O)N(R)OR,    —OC(O)R, —OC(O)NR₂, —N(R)C(O)OR, —N(R)C(O)R, —N(R)C(O)NR₂,    —N(R)S(O)₂R, or —N(R)S(O)₂NR₂; or two instances of R⁴ may be taken    together with the atoms to which they are attached to form a C₄₋₈    partially unsaturated carbocyclic ring;-   each R⁵ is independently R, halogen, —CN, —NO₂, —OR, —SR, —NR₂,    —S(O)₂R, —S(O)₂NR₂, —S(O)R, —C(O)R, —C(O)OR, —C(O)NR₂, —C(O)N(R)OR,    —OC(O)R, —OC(O)NR₂, —N(R)C(O)OR, —N(R)C(O)R, —N(R)C(O)NR₂,    —N(R)S(O)₂R, or —N(R)S(O)₂NR₂; or two instances of R⁵ may be taken    together to form ═O or ═S;-   each R⁶ is independently hydrogen or C₁₋₆ alkyl optionally    substituted with 1, 2, 3, 4, 5, or 6 deuterium or halogen atoms;-   each R⁷ is independently R, halogen, —CN, —NO₂, —OR, —SR, —NR₂,    —S(O)₂R, —S(O)₂NR₂, —S(O)R, —C(O)R, —C(O)OR, —C(O)NR₂, —C(O)N(R)OR,    —OC(O)R, —OC(O)NR₂, —N(R)C(O)OR, —N(R)C(O)R, —N(R)C(O)NR₂,    —N(R)S(O)₂R, or —N(R)S(O)₂NR₂; or two instances of R⁴ may be taken    together with the atoms to which they are attached to form a C₄₋₈    partially unsaturated carbocyclic ring;-   each R is independently hydrogen or an optionally substituted group    selected from C₁₋₆ aliphatic, a 3-8 membered saturated or partially    unsaturated monocyclic carbocyclic ring, phenyl, an 8-10 membered    bicyclic aromatic carbocyclic ring, a 4-8 membered saturated or    partially unsaturated monocyclic heterocyclic ring having 1-2    heteroatoms independently selected from nitrogen, oxygen, or sulfur,    a 5-6 membered monocyclic heteroaromatic ring having 1-4 heteroatoms    independently selected from nitrogen, oxygen, or sulfur, or an 8-10    membered bicyclic heteroaromatic ring having 1-5 heteroatoms    independently selected from nitrogen, oxygen, or sulfur;-   L² is a C₁₋₂₀ bivalent or trivalent, straight or branched,    optionally substituted hydrocarbon chain wherein 1, 2, 3, 4, 5, 6,    7, 8, 9, or 10 methylene units of the chain are independently and    optionally replaced with a natural or non-natural amino acid, —O—,    —C(O)—, —C(O)O—, —OC(O)—, —N(R)—, —C(O)N(R)—, —(R)NC(O)—,    —OC(O)N(R)—, —(R)NC(O)O—, —N(R)C(O)N(R)—, —S—, —SO—, —SO₂—,    —SO₂N(R)—, —(R)NSO₂—, —C(S)—, —C(S)O—, —OC(S)—, —C(S)N(R)—,    —(R)NC(S)—, —(R)NC(S)N(R)—, or -Cy-; and 1-20 of the methylene units    of the chain are independently and optionally replaced with    —OCH₂CH₂—;-   each -Cy- is independently a bivalent optionally substituted 3-8    membered saturated or partially unsaturated monocyclic carbocyclic    ring, optionally substituted phenylene, an optionally substituted    4-8 membered saturated or partially unsaturated monocyclic    heterocyclic ring having 1-3 heteroatoms independently selected from    nitrogen, oxygen, or sulfur, an optionally substituted 5-6 membered    monocyclic heteroaromatic ring having 1-4 heteroatoms independently    selected from nitrogen, oxygen, or sulfur, an optionally substituted    8-10 membered bicyclic or bridged bicyclic saturated or partially    unsaturated heterocyclic ring having 1-5 heteroatoms independently    selected from nitrogen, oxygen, or sulfur, or an optionally    substituted 8-10 membered bicyclic or bridged bicyclic    heteroaromatic ring having 1-5 heteroatoms independently selected    from nitrogen, oxygen, or sulfur;-   m is 0, 1, 2, 3, or 4; and-   p is 0, 1, 2, 3, or 4.

As defined generally above, Ar¹ is an optionally substituted phenyl oroptionally substituted 5-6 membered monocyclic heteroaromatic ringhaving 1-4 heteroatoms independently selected from nitrogen, oxygen, orsulfur.

In some embodiments, Ar¹ is an optionally substituted phenyl. In someembodiments, Ar¹ is an optionally substituted 5-6 membered monocyclicheteroaromatic ring having 1-4 heteroatoms independently selected fromnitrogen, oxygen, or sulfur.

In some embodiments, Ar¹ is phenyl optionally subsituted with 1, 2, 3,or 4 substituents selected from halogen, —C₁₋₆ aliphatic, —CN, —OR,—NR₂, —CO₂R, —C(O)R, —SR, or —C(O)NR₂. In some embodiments, the optionalsubstituents are selected from halogen, —CN, —C₁₋₆ alkyl, or —OMe. Insome embodiments, at least one of the optional substituents is C₁₋₆alkyl. In some embodiments, 1, 2, or 3 substituents are present. In someembodiments, Ar¹ is selected from those depicted in Table 5, below.

As defined generally above, Ar³ is an optionally substituted phenyl, anoptionally substituted 5-6 membered monocyclic heteroaromatic ringhaving 1-4 heteroatoms independently selected from nitrogen, oxygen, orsulfur, an optionally substituted 8-12 membered bicyclic aromatic ring,or an optionally substituted 8-10 membered bicyclic heteroaromatic ringhaving 1-5 heteroatoms independently selected from nitrogen, oxygen, orsulfur.

In some embodiments, Ar³ is an optionally substituted phenyl. In someembodiments, Ar³ is an optionally substituted 5-6 membered monocyclicheteroaromatic ring having 1-4 heteroatoms independently selected fromnitrogen, oxygen, or sulfur. In some embodiments, Ar³ is an optionallysubstituted 8-12 membered bicyclic aromatic ring. In some embodiments,Ar³ is an optionally substituted 8-10 membered bicyclic heteroaromaticring having 1-5 heteroatoms independently selected from nitrogen,oxygen, or sulfur.

In some embodiments, Ar³ is an optionally substituted pyridinyl,pyrimidinyl, imidazolyl, or pyrrolyl. In some embodiments, Ar³ is anoptionally substituted pyridinyl. In some embodiments, Ar³ is pyridinyl.In some embodiments, the optional substituents are selected fromhalogen, —C₁₋₆ aliphatic, —CN, —OR, —NR₂, —CO₂R, —C(O)R, —SR, or—C(O)NR₂.

In some embodiments, Ar³ is phenyl optionally subsituted with 1, 2, 3,or 4 substituents selected from halogen, —C₁₋₆ aliphatic, —CN, —OR,—NR₂, —CO₂R, —C(O)R, —SR, or —C(O)NR₂. In some embodiments, the optionalsubstituents are selected from halogen, —CN, —C₁₋₆ alkyl, or —OMe. Insome embodiments, at least one of the optional substituents is halogen.In some embodiments, 1, 2, or 3 substituents are present. In someembodiments, Ar³ is phenyl subsituted with 3 substituents selected fromhalogen, —C₁₋₆ aliphatic, and —OR. In some embodiments, Ar³ is selectedfrom those depicted in Table 5, below.

As defined generally above, X is selected from a bivalent C₁₋₃ alkylenechain wherein 1-2 methylene units of the chain are independently andoptionally replaced with —O—, —NR⁶—, —S—, —C(O)—, —CO₂——CS—, —C(NR⁶)—,—S(O)—, or —S(O)₂—.

In some embodiments, X is a bivalent C₁₋₃ alkylene chain wherein 1-2methylene units of the chain are independently and optionally replacedwith —O—, —NR⁶—, —S—, —C(O)—, —CO₂——CS—, —C(NR⁶)—, —S(O)—, or —S(O)₂—.In some embodiments, X is —O—, —NR⁶—, —S—, —C(O)—, —CO₂——CS—, —C(NR⁶)—,—S(O)—, r —S(O)₂—(i.e., a C₁ alkylene wherein the methylene unit isreplaced with —O—, —NR⁶—, etc.). In some embodiments, X is a bivalentC₁₋₂ alkylene chain wherein one methylene unit of the chain isoptionally replaced with —O—, —S—, —C(O)—, —CO₂——CS—, —C(NR⁶)-, —S(O)—,or —S(O)₂—. In some embodiments, X is —O—, —C(O)—, —C(O)—O—, —O—C(O)—,—NH—C(O)—, or —C(O)—NH—. In some embodiments, X is selected from thosedepicted in Table 5, below.

As defined generally above, X² is selected from a bivalent C₁₋₃ alkylenechain wherein 1-2 methylene units of the chain are independently andoptionally replaced with —O—, —NR⁶—, —S—, —C(O)—, —CO₂——CS—, —C(NR⁶)—,—S(O)—, or —S(O)₂—.

In some embodiments, X² is a bivalent C₁₋₃ alkylene chain wherein 1-2methylene units of the chain are independently and optionally replacedwith —O—, —NR⁶—, —S—, —C(O)—, —CO₂——CS—, —C(NR⁶)—, —S(O)—, or —S(O)₂—.In some embodiments, X² is —O—, —NR⁶—, —S—, —C(O)—, —CO₂——CS—, —C(NR⁶)—,—S(O)—, or —S(O)₂—(i.e., a C₁ alkylene wherein the methylene unit isreplaced with —O—, —NR⁶—, etc.). In some embodiments, X² is a bivalentC₁₋₂ alkylene chain wherein one methylene unit of the chain isoptionally replaced with —O—, —NR⁶—, —S—, —C(O)—, —CO₂——CS—, —C(NR⁶)—,—S(O)—, or —S(O)₂—. In some embodiments, X² is —CH₂—NH-, —OCH₂—, —CH₂O—,—O—, —C(O)—, —C(O)—O—, —O—C(O)—, —NH—C(O)—, or —C(O)—NH-. In someembodiments, X² is selected from those depicted in Table 5, below.

As defined generally above, R² is a photoactivatable group thatoptionally comprises a click-ready group if R³ is absent. In someembodiments, R² is a photoactivatable group. In some embodiments, R² isa photoactivatable group further substituted with a click-ready group.

In some embodiments, R² is a functional group that generates a radical,an aryl or heteroaryl carbocation, a nitrene, or a carbene intermediateupon irradiation with ultraviolet (UV) radiation, and that is optionallysubstituted with a click-ready group or pull-down group if R³ is absent.In some embodiments, R² is an optionally substituted phenyl or 8-10membered bicyclic aromatic carbocyclic azide or 5-8 membered heteroarylor 8-10 membered bicyclic heteroaryl azide, optionally substitutedbenzoyl azide or 5-8 membered heteroaroyl azide or 8-10 memberedheteroaroyl azide wherein 1-3 atoms of the ring atoms are selected fromnitrogen, sulfur, or oxygen, optionally substituted phenyl or 8-10membered bicyclic aromatic carbocyclic diazonium salt, optionallysubstituted 5-8 membered heteroaryl or 8-10 membered bicyclic heteroaryldiazonium salt wherein 1-3 atoms of the ring atoms are selected fromnitrogen, sulfur, or oxygen, optionally substituted C₂₋₆ aliphatic diazofunctional group, optionally substituted C₂₋₆ aliphatic diazirine, oroptionally substituted diphenyl or 8-10-membered diheteroaryl ketonewherein 1-3 atoms of the ring atoms are selected from nitrogen, sulfur,or oxygen, optionally substituted dihydropyrene, optionally substitutedspirooxazine, optionally substituted anthracene, optionally substitutedfulgide, optionally substituted spiropyran, optionally substitutedα-pyrone or optionally substituted pyrimidone; and which is optionallysubstituted with a click-ready group or pull-down group. In someembodiments, the click-ready group is a C₁₋₆ alkyl azide or alkyne. Insome embodiments, R² is selected from

wherein Y⁻ is a pharmaceutically acceptable anion.

In some embodiments, R² is selected from those depicted in Table 5,below.

As defined generally above, R³ is absent or is a click-ready group or apull-down group. In some embodiments, R³ is absent. In some embodiments,R³ is a click-ready group. In some embodiments, R³ is a pull-down group.In some embodiments, R³ is a C₁₋₆ alkyl azide, C₁₋₆ alkyne, or a haptensuch as biotin.

In some embodiments, R³ is selected from those depicted in Table 5,below.

As defined generally above, each R⁴ is independently R, halogen, —CN,—NO₂, —OR, —SR, —NR₂, —S(O)₂R, —S(O)₂NR₂, —S(O)R, —C(O)R, —C(O)OR,—C(O)NR₂, —C(O)N(R)OR, —OC(O)R, —OC(O)NR₂, —N(R)C(O)OR, —N(R)C(O)R,—N(R)C(O)NR₂, —N(R)S(O)₂R, or —N(R)S(O)₂NR₂; or two instances of R⁴ maybe taken together with the atoms to which they are attached to form aC₄₋₈ partially unsaturated carbocyclic ring.

In some embodiments, R⁴ is R. In some embodiments, R⁴ is halogen. Insome embodiments, R⁴ is —CN. In some embodiments, R⁴ is —NO_(2.) In someembodiments, R⁴ is —OR.

In some embodiments, R⁴ is —SR. In some embodiments, R⁴ is —NR₂. In someembodiments, R⁴ is —S(O)₂R. In some embodiments, R⁴ is —S(O)₂NR₂. Insome embodiments, R⁴ is —S(O)R. In some embodiments, R⁴ is —C(O)R. Insome embodiments, R⁴ is —C(O)OR. In some embodiments, R⁴ is —C(O)NR₂. Insome embodiments, R⁴ is —C(O)N(R)OR. In some embodiments, R⁴ is —OC(O)R.In some embodiments, R⁴ is —OC(O)NR₂. In some embodiments, R⁴ is—N(R)C(O)OR. In some embodiments, R⁴ is —N(R)C(O)R. In some embodiments,R⁴ is —N(R)C(O)NR₂. In some embodiments, R⁴ is —N(R)S(O)₂R. In someembodiments, R⁴ is —N(R)S(O)₂NR₂. In some embodiments, two instances ofR⁴ are taken together with the atoms to which they are attached to forma C₄₋₈ partially unsaturated carbocyclic ring.

In some embodiments, R⁴ is hydrogen, C₁₋₆ aliphatic, a 3-8 memberedsaturated or partially unsaturated monocyclic carbocyclic ring, phenyl,an 8-10 membered bicyclic aromatic carbocyclic ring, a 4-8 memberedsaturated or partially unsaturated monocyclic heterocyclic ring having1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur;a 5-6 membered monocyclic heteroaromatic ring having 1-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; an 8-10membered bicyclic heteroaromatic ring having 1-5 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; halogen, —CN,—NO₂, —OR, —SR, —NR₂, —S(O)₂R, —S(O)₂NR₂, —S(O)R, —C(O)R, —C(O)OR,—C(O)NR₂, —OC(O)R, or —N(R)C(O)R.

In some embodiments, R⁴ is hydrogen, C₁₋₆ alkyl optionally substitutedwith 1, 2, 3, 4, 5, or 6 deuterium or halogen atoms; a 3-8 memberedsaturated or partially unsaturated monocyclic carbocyclic ring, phenyl,a 4-8 membered saturated or partially unsaturated monocyclicheterocyclic ring having 1-2 heteroatoms independently selected fromnitrogen, oxygen, or sulfur; a 5-6 membered monocyclic heteroaromaticring having 1-4 heteroatoms independently selected from nitrogen,oxygen, or sulfur; halogen, —CN, —OR, —NR₂, —S(O)₂NR₂, —C(O)R, —C(O)OR,—C(O)NR₂, —OC(O)R, or —N(R)C(O)R. In some embodiments, R⁴ is hydrogen,C₁₋₆ alkyl, phenyl, halogen, —CN, —OR, or —NR₂. In some embodiments, R⁴is selected from those depicted in Table 5, below.

As defined generally above, each R⁵ is independently R, halogen, —CN,—NO₂, —OR, —SR, —NR₂, —S(O)₂R, —S(O)₂NR₂, —S(O)R, —C(O)R, —C(O)OR,—C(O)NR₂, —C(O)N(R)OR, —OC(O)R, —OC(O)NR₂, —N(R)C(O)OR, —N(R)C(O)R,—N(R)C(O)NR₂, —N(R)S(O)₂R, or —N(R)S(O)₂NR₂; or two instances of R⁵ maybe taken together to form ═O or ═S.

In some embodiments, R⁵ is R. In some embodiments, R⁵ is halogen. Insome embodiments, R⁵ is —CN. In some embodiments, R⁵ is —NO₂. In someembodiments, R⁵ is —OR. In some embodiments, R⁵ is —SR. In someembodiments, R⁵ is —NR₂. In some embodiments, R⁵ is —S(O)₂R. In someembodiments, R⁵ is —S(O)₂NR₂. In some embodiments, R⁵ is —S(O)R. In someembodiments, R⁵ is —C(O)R. In some embodiments, R⁵ is —C(O)OR. In someembodiments, R⁵ is —C(O)NR₂. In some embodiments, R⁵ is —C(O)N(R)OR. Insome embodiments, R⁵ is —OC(O)R. In some embodiments, R⁵ is —OC(O)NR₂.In some embodiments, R⁵ is —N(R)C(O)OR. In some embodiments, R⁵ is—N(R)C(O)R. In some embodiments, R⁵ is —N(R)C(O)NR₂. In someembodiments, R⁵ is —N(R)S(O)₂R. In some embodiments, R⁵ is—N(R)S(O)₂NR₂. In some embodiments, two instances of R⁵ are takentogether to form ═O or ═S.

In some embodiments, R⁵ is hydrogen, C₁₋₆ aliphatic, a 3-8 memberedsaturated or partially unsaturated monocyclic carbocyclic ring, phenyl,an 8-10 membered bicyclic aromatic carbocyclic ring, a 4-8 memberedsaturated or partially unsaturated monocyclic heterocyclic ring having1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur;a 5-6 membered monocyclic heteroaromatic ring having 1-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; an 8-10membered bicyclic heteroaromatic ring having 1-5 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; halogen, —CN,—NO₂, —OR, —SR, —NR₂, —S(O)₂R, —S(O)₂NR₂, —S(O)R, —C(O)R, —C(O)OR,—C(O)NR₂, —OC(O)R, or —N(R)C(O)R.

In some embodiments, R⁵ is hydrogen, C₁₋₆ alkyl optionally substitutedwith 1, 2, 3, 4, 5, or 6 deuterium or halogen atoms; a 3-8 memberedsaturated or partially unsaturated monocyclic carbocyclic ring, phenyl,a 4-8 membered saturated or partially unsaturated monocyclicheterocyclic ring having 1-2 heteroatoms independently selected fromnitrogen, oxygen, or sulfur; a 5-6 membered monocyclic heteroaromaticring having 1-4 heteroatoms independently selected from nitrogen,oxygen, or sulfur; halogen, —CN, —OR, —NR₂, —S(O)₂NR₂, —C(O)R, —C(O)OR,—C(O)NR₂, —OC(O)R, or —N(R)C(O)R. In some embodiments, R⁵ is hydrogen,C₁₋₆ alkyl, phenyl, halogen, —CN, —OR, or —NR₂.

As defined generally above, each R⁶ is independently hydrogen or C₁₋₆alkyl optionally substituted with 1, 2, 3, 4, 5, or 6 deuterium orhalogen atoms.

In some embodiments, R⁶ is hydrogen. In some embodiments, R⁶ is C₁₋₆alkyl optionally substituted with 1, 2, 3, 4, 5, or 6 deuterium orhalogen atoms.

In some embodiments, R⁶ is C₁₋₃ alkyl optionally substituted with 1, 2,or 3 halogen atoms.

In some embodiments, R⁶ is selected from those depicted in Table 5,below.

As defined generally above, each R⁷ is independently R, halogen, —CN,—NO₂, —OR, —SR, —NR₂, —S(O)₂R, —S(O)₂NR₂, —S(O)R, —C(O)R, —C(O)OR,—C(O)NR₂, —C(O)N(R)OR, —OC(O)R, —OC(O)NR₂, —N(R)C(O)OR, —N(R)C(O)R,—N(R)C(O)NR₂, —N(R)S(O)₂R, or —N(R)S(O)₂NR₂; or two instances of R⁷ maybe taken together with the atoms to which they are attached to form aC₄₋₈ partially unsaturated carbocyclic ring.

In some embodiments, R⁷ is R. In some embodiments, R⁷ is halogen. Insome embodiments, R⁷ is —CN. In some embodiments, R⁷ is —NO_(2.) In someembodiments, R⁷ is —OR. In some embodiments, R⁷ is —SR. In someembodiments, R⁷ is —NR₂. In some embodiments, R⁷ is —S(O)₂R. In someembodiments, R⁷ is —S(O)₂NR₂. In some embodiments, R⁷ is —S(O)R. In someembodiments, R⁷ is —C(O)R. In some embodiments, R⁷ is —C(O)OR. In someembodiments, R⁷ is —C(O)NR₂. In some embodiments, R⁷ is —C(O)N(R)OR. Insome embodiments, R⁷ is —OC(O)R. In some embodiments, R⁷ is —OC(O)NR₂.In some embodiments, R⁷ is —N(R)C(O)OR. In some embodiments, R⁷ is—N(R)C(O)R. In some embodiments, R⁷ is —N(R)C(O)NR₂. In someembodiments, R⁷ is —N(R)S(O)₂R. In some embodiments, R⁷ is—N(R)S(O)₂NR₂. In some embodiments, two instances of R⁷ are takentogether with the atoms to which they are attached to form a C₄₋₈partially unsaturated carbocyclic ring.

In some embodiments, R⁷ is hydrogen, C₁₋₆ aliphatic, a 3-8 memberedsaturated or partially unsaturated monocyclic carbocyclic ring, phenyl,an 8-10 membered bicyclic aromatic carbocyclic ring, a 4-8 memberedsaturated or partially unsaturated monocyclic heterocyclic ring having1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur;a 5-6 membered monocyclic heteroaromatic ring having 1-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; an 8-10membered bicyclic heteroaromatic ring having 1-5 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; halogen, —CN,—NO₂, —OR, —SR, —NR₂, —S(O)₂R, —S(O)₂NR₂, —S(O)R, —C(O)R, —C(O)OR,—C(O)NR₂, —OC(O)R, or —N(R)C(O)R.

In some embodiments, R⁷ is hydrogen, C₁₋₆ alkyl optionally substitutedwith 1, 2, 3, 4, 5, or 6 deuterium or halogen atoms; a 3-8 memberedsaturated or partially unsaturated monocyclic carbocyclic ring, phenyl,a 4-8 membered saturated or partially unsaturated monocyclicheterocyclic ring having 1-2 heteroatoms independently selected fromnitrogen, oxygen, or sulfur; a 5-6 membered monocyclic heteroaromaticring having 1-4 heteroatoms independently selected from nitrogen,oxygen, or sulfur; halogen, —CN, —OR, —NR₂, —S(O)₂NR₂, —C(O)R, —C(O)OR,—C(O)NR₂, —OC(O)R, or —N(R)C(O)R. In some embodiments, R⁷ is hydrogen,C₁₋₆ alkyl, phenyl, halogen, —CN, —OR, or —NR₂. In some embodiments, R⁷is selected from those depicted in Table 5, below.

As defined generally above, L² is a C₁₋₂₀ bivalent or trivalent,straight or branched, optionally substituted hydrocarbon chain wherein1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 methylene units of the chain areindependently and optionally replaced with a natural or non-naturalamino acid, —O—, —C(O)—, —C(O)O—, —OC(O)—, —N(R)—, —C(O)N(R)—,—(R)NC(O)—, —OC(O)N(R)—, —(R)NC(O)O—, —N(R)C(O)N(R)—, —S—, —SO—,—SO₂N(R)—, —(R)NSO₂—, —C(S)—, —C(S)O—, —OC(S)—, —C(S)N(R)—, —(R)NC(S)—,—(R)NC(S)N(R)—, or -Cy-; and 1-20 of the methylene units of the chainare independently and optionally replaced with —OCH₂CH₂—.

In some embodiments, L² is a C₁₋₁₀ bivalent or trivalent, straight orbranched, optionally substituted hydrocarbon chain wherein 1, 2, 3, 4,or 5 methylene units of the chain are independently and optionallyreplaced with a natural or non-natural amino acid, —O—, —C(O)—, —C(O)O—,—OC(O)—, —N(R)—, —C(O)N(R)—, —(R)NC(O)—, —OC(O)N(R)—, —(R)NC(O)O—,—N(R)C(O)N(R)—, —S—, —SO—, —SO₂N(R)—, —(R)NSO₂—, —C(S)—, —C(S)O—,—OC(S)—, —C(S)N(R)—, —(R)NC(S)—, —(R)NC(S)N(R)—, or -Cy-; and 1-5 of themethylene units of the chain are independently and optionally replacedwith —OCH₂CH₂—. In some embodiments, L² comprises 1-3 natural aminoacids. In some embodiments, the amino acids are selected from proline,lysine, glycine, or alanine. In some embodiments, L² comprises 1-2-Cy-groups selected from 1,2,3-triazolylene or 1,2,4-triazolylene. In someembodiments, L² comprises 1-10, 1-8, 1-6, 1-4, 1-3, 1-2, 1, 2, or 3—OCH₂CH₂— units.

In some embodiments, L² is a C₁₋₂₀ bivalent or trivalent, straight orbranched, optionally substituted hydrocarbon chain wherein 1, 2, 3, 4,or 5 methylene units of the chain are independently and optionallyreplaced with —O—, —C(O)—, —C(O)O—, —OC(O)—, —N(R)—, —C(O)N(R)—,—(R)NC(O)—, —S—, —SO—, —SO₂—, —C(S)—, or -Cy-; and 1-20 of the methyleneunits of the chain are independently and optionally replaced with—OCH₂CH₂—.

In some embodiments, L² is a C₁₋₂₀ bivalent or trivalent, straight,optionally substituted hydrocarbon chain wherein 1, 2, 3, 4, or 5methylene units of the chain are independently and optionally replacedwith —O—, —C(O)—, —N(R)—, or -Cy-; and 1-20 of the methylene units ofthe chain are independently and optionally replaced with —OCH₂CH₂—.

In some embodiments, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or15 methylene units of the chain are replaced with —OCH₂CH₂—. In someembodiments, 1, 2, 3, 4, 5, 6, 7, or 8; or 1, 2, 3, 4, or 5 methyleneunits of the chain are replaced with —OCH₂CH₂—.

In some embodiments, L² is selected from those depicted in Table 5,below.

As defined generally above, each -Cy- is independently a bivalentoptionally substituted 3-8 membered saturated or partially unsaturatedmonocyclic carbocyclic ring, optionally substituted phenylene, anoptionally substituted 4-8 membered saturated or partially unsaturatedmonocyclic heterocyclic ring having 1-3 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur, an optionally substituted 5-6membered monocyclic heteroaromatic ring having 1-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur, an optionallysubstituted 8-10 membered bicyclic or bridged bicyclic saturated orpartially unsaturated heterocyclic ring having 1-5 heteroatomsindependently selected from nitrogen, oxygen, or sulfur, or anoptionally substituted 8-10 membered bicyclic or bridged bicyclicheteroaromatic ring having 1-5 heteroatoms independently selected fromnitrogen, oxygen, or sulfur.

In some embodiments, -Cy- is a bivalent optionally substituted 3-8membered saturated or partially unsaturated monocyclic carbocyclic ring.In some embodiments, -Cy- is an optionally substituted phenylene. Insome embodiments, -Cy- is an optionally substituted 4-8 memberedsaturated or partially unsaturated monocyclic heterocyclic ring having1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur.In some embodiments, -Cy- is an optionally substituted 5-6 memberedmonocyclic heteroaromatic ring having 1-4 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur. In some embodiments, -Cy- isan optionally substituted 8-10 membered bicyclic or bridged bicyclicsaturated or partially unsaturated heterocyclic ring having 1-5heteroatoms independently selected from nitrogen, oxygen, or sulfur. Insome embodiments, -Cy- is an optionally substituted 8-10 memberedbicyclic or bridged bicyclic heteroaromatic ring having 1-5 heteroatomsindependently selected from nitrogen, oxygen, or sulfur.

In some embodiments, -Cy- is phenylene, pyridinylene, pyrimidinylene,1,2,3-triazolylene, or 1,2,4-triazolylene.

In some embodiments, -Cy- is selected from those depicted in Table 5,below.

As defined generally above, m is 0, 1, 2, 3, or 4. In some embodiments,m is 0. In some embodiments, m is 1. In some embodiments, m is 2. Insome embodiments, m is 3. In some embodiments, m is 4. In someembodiments, m is 0, 1, 2, or 3. In some embodiments, m is 0, 1, or 2.In some embodiments, m is 1 or 2.

As defined generally above, p is 0, 1, 2, 3, or 4. In some embodiments,p is 0. In some embodiments, p is 1. In some embodiments, p is 2. Insome embodiments, p is 3. In some embodiments, p is 4. In someembodiments, p is 0, 1, 2, or 3. In some embodiments, p is 0, 1, or 2.In some embodiments, p is 1 or 2.

In some embodiments, the present invention provies a compound ofFormulae X-c, X-d, X-e, or X-f:

or a tautomer or pharmaceutically acceptable salt thereof, wherein eachof Ar¹ , Ar², X, L¹, R¹, R², R³, R⁶, R, -Cy-, and n is as defined aboveand described in embodiments herein, both singly and in combination.

In some embodiments, the present invention provides a compound ofFormulae XI or XII:

or a tautomer or pharmaceutically acceptable salt thereof, wherein eachof Ar¹ , Ar², X, L¹, R¹, R², R³, R⁶, R, -Cy-, and n is as defined aboveand described in embodiments herein, both singly and in combination.

In some embodiments, the present invention provides a compound ofFormula XIII:

or a tautomer or pharmaceutically acceptable salt thereof, wherein eachof Ar¹, Ar², R¹, R², R⁶, R, and -Cy- is as defined above and describedin embodiments herein, both singly and in combination.

In some embodiments, the present invention provides a compound ofFormula XIV:

or a tautomer or pharmaceutically acceptable salt thereof, wherein eachof X, L¹, R¹, R², R³, R⁶, R, -Cy-, and n is as defined above anddescribed in embodiments herein, both singly and in combination.

In some embodiments, the present invention provides a compound ofFormula XV:

or a tautomer or pharmaceutically acceptable salt thereof, wherein eachof X, L¹, R¹, R², R³, R⁶, R, -Cy-, and n is as defined above anddescribed in embodiments herein, both singly and in combination.

In some embodiments, the present invention provides a compound ofFormulae XVI, XVII, XVIII, or XIX:

or a tautomer or pharmaceutically acceptable salt thereof, wherein eachof L¹, R¹, R², R³, R⁶, R, -Cy-, and n is as defined above and describedin embodiments herein, both singly and in combination.

In some embodiments, the present invention provides a compound ofFormulae XX, XXI, XXII, XXIII, or XXIV:

or a tautomer or pharmaceutically acceptable salt thereof, wherein eachof R², R³, R⁶, R, -Cy-, and n is as defined above and described inembodiments herein, both singly and in combination.

In some embodiments, the present invention provides a compound ofFormulae XXVII or XXVIII:

or a pharmaceutically acceptable salt thereof, wherein each of Ar¹ ,Ar³, X, X², L², R², R³, R⁴, R⁵, R⁶, R, -Cy-, m, and p is as definedabove and described in embodiments herein, both singly and incombination.

In some embodiments, the present invention provides a compound ofFormulae XXIX, XXX, XXXI, XXXII, or XXXIII:

or a pharmaceutically acceptable salt thereof, wherein each of X, X²,L², R², R³, R⁴, R⁶, R, -Cy-, and m is as defined above and described inembodiments herein, both singly and in combination.

In some embodiments, the present invention provides a compound ofFormulae XXXIV, XXXV, XXXVI, or XXXVII:

or a pharmaceutically acceptable salt thereof, wherein each of Ar¹, Ar³,X, X², L², R², R³, R⁴, R⁶, R⁷, R, -Cy-, m, and p is as defined above anddescribed in embodiments herein, both singly and in combination.

In some embodiments, the present invention provides a compound ofFormulae XXXVIII, XXXIX, XL, XLI, or XLII:

or a pharmaceutically acceptable salt thereof, wherein each of X, L²,R², R³, R⁴, R⁶, R⁷, R, -Cy-, m, and p is as defined above and describedin embodiments herein, both singly and in combination.

Exemplary compounds of the invention are set forth in Table 5, below.

TABLE 5 Exemplary Compounds

I-1 (ARK-139)

I-2 (ARK-673)

I-3 (ARK-674)

I-4 (ARK-672)

I-5 (ARK-544)

I-6 (ARK-546)

I-7 (ARK-547)

I-8 (ARK-549)

I-9 (ARK-579)

I-10 (ARK-580)

I-11 (ARK-581)

I-12

I-13 (ARK-670)

I-14 (ARK-729)

I-15 (ARK-816)

I-16 (ARK-671)

I-17 (ARK-669)

I-18 (ARK-668)

I-19

I-20

I-21

I-22

I-23

I-24

I-25

I-26

I-27

I-28

I-29

I-30

I-31

I-32

I-33

I-34

I-35

I-36

In some embodiments, the present invention provides a compound set forthin Table 1, above, or a pharmaceutically acceptable salt thereof.

In some embodiments, the compound or conjugate is selected from thoseformulae shown in FIGS. 1-44, or a pharmaceutically acceptable salt,stereoisomer, or tautomer thereof.

Small Molecule RNA Ligands

The design and synthesis of novel, small molecule ligands capable ofbinding RNA represents largely untapped therapeutic potential. In someembodiments, the small molecule ligand is selected from a compound knownto bind to RNA, such as a heteroaryldihydropyrimidine (HAP), a macrolide(e.g., erythromycin, azithromycin), alkaloid (e.g., berberine,palmatine), aminoglycoside (e.g., paromomycin, neomycin B, kanamycin A),tetracycline (e.g., doxycycline, oxytetracycline), a theophylline,ribocil, clindamycin, chloramphenicol, LMI070, a triptycene-basedscaffold, an oxazolidinone (e.g., linezolid, tedizolid), or CPNQ.

In some embodiments, the small molecule ligand is ribocil, which has thefollowing structure:

or a pharmaceutically acceptable salt thereof Ribocil is a a drug-likeligand that binds to the FMN riboswitch (PDB 5KX9) and inhibitsriboswitch function (Nature 2015, 526, 672-677).

In some embodiments, the small molecule ligand is an oxazolidinone suchas linezolid, tedizolid, eperezolid, or PNU 176798. Exemplaryoxazolidinone-based photoprobes are described in, e.g., Matassova, N. B.et al., RNA (1999), 5:939-946; Leach, K. L. et al., Molecular Cell 2007,26, 393-402; Colca, J. R. et al., J. Biol. Chem. 2003, 278 (24),21972-21979; and each of which is hereby incorporated by reference. Suchoxazolidinones include the following:

The foregoing oxazolidinones may be substituted with a photoactivatablegroup as described herein at any available position, optionally with atether linking the photoactivatable group with the oxazolidinone. Azidephotoactivatable groups are optionally replaced with otherphotoactivatable groups described herein. The asterisks (*) indicate theposition of a ¹²⁵I or ¹⁴C radioligand used in the original reference,and which is optional for use as a pull-down group in the presentinvention.

Aryldiazonium salts, for example thep-diazonium anilide ofL—S—carboxyspermine and L-₂—carboxyputrescine, have also been shown tobe useful as photoactivatable probes for RNA mapping and footprinting ofRNA/protein interaction. See, e.g., Garcia, A. et al., Nucleic AcidsRes. 1990, 18 (1), 89-95.

Furthermore, certain compounds comprising a quinoline core, of whichCPNQ is one, are capable of binding RNA. CPNQ has the followingstructure:

Accordingly, in some embodiments, the small molecule ligand is selectedfrom CPNQ or a pharmaceutically acceptable salt thereof. In otherembodiments, the ligand is selected from a quinoline compound related toCPNQ, such as those provided in any one of FIG. 36 or 39-43; or apharmaceutically acceptable salt thereof.

In some embodiments, CPNQ or a quinoline related to CPNQ is modified atone or more available positions to replace a hydrogen with a tether(-T¹-and/or -T²-), click-ready group (—R^(CG)), or warhead (—R^(mod)),according to embodiments of each as described herein. For example, CPNQor a quinoline related to CPNQ may have one of the following formulae:

or a pharmaceutically acceptable salt thereof; wherein R^(mod) isoptionally substituted with —R^(CG) or -T₂-R^(CG), and furtheroptionally substituted with a pull-down group. The compound of formulaeIX-a or IX-b may further be optionally substituted with one or moreoptional substituents, as defined below, such as 1 or 2 optionalsubstituents.

Organic dyes, amino acids, biological cofactors, metal complexes as wellas peptides also show RNA binding ability. It is possible to modulateRNAs such as riboswitches, RNA molecules with expanded nucleotiderepeats, and viral RNA elements.

The term “small molecule that binds a target RNA,” “small molecule RNAbinder,” “affinity moiety,” “ligand,” or “ligand moiety,” as usedherein, includes all compounds generally classified as small moleculesthat are capable of binding to a target RNA with sufficient affinity andspecificity for use in a disclosed method, or to treat, prevent, orameliorate a disease associated with the target RNA. Small moleculesthat bind RNA for use in the present invention may bind to one or moresecondary or tertiary structure elements of a target RNA. These sitesinclude RNA triplexes, hairpins, bulge loops, pseudoknots, internalloops, junctions, and other higher-order RNA structural motifs describedor referred to herein.

Accordingly, in some embodiments, the small molecule that binds to atarget RNA (e.g., Ligand in Formulae I-VIII above) is selected from aheteroaryldihydropyrimidine (HAP), a macrolide, alkaloid,aminoglycoside, a member of the tetracycline family, an oxazolidinone, aSMN2 pre-mRNA ligand such as LMI070 (NVS-SM1), ribocil or an analoguethereof, clindamycin, chloramphenicol, an anthracene, a triptycene,theophylline or an analogue thereof, or CPNQ or an analogue thereof Insome embodiments, the small molecule that binds to a target RNA isselected from paromomycin, a neomycin (such as neomycin B), a kanamycin(such as kanamycin A), linezolid, tedizolid, pleuromutilin, ribocil,anthracene, triptycene, or CPNQ or an analogue thereof wherein eachsmall molecule may be optionally substituted with one or more “optionalsubstituents” as defined below, such as 1, 2, 3, or 4, for example 1 or2, optional substituents. In some embodiments, the small molecule isselected from those shown in FIG. 1-8 or 18-44, or a pharmaceuticallyacceptable salt, stereoisomer, or tautomer thereof.

In some embodiments, the Ligand is selected from

or a pharmaceutically acceptable salt thereof

In some embodiments, the Ligand binds to a junction, stem-loop, or bulgein a target RNA. In some embodiments, Ligand binds to a nucleic acidthree-way junction (3WJ). In some embodiments, the 3WJ is a trans 3WJbetween two RNA molecules. In some embodiments, the 3WJ is a trans 3WJbetween a miRNA and mRNA. In some embodiments, the Ligand binds to DNA,such as a DNA loop or junction.

Compounds of the present invention include those described generallyherein, and are further illustrated by the classes, subclasses, andspecies disclosed herein. As used herein, the following definitionsshall apply unless otherwise indicated. For purposes of this invention,the chemical elements are identified in accordance with the PeriodicTable of the Elements, CAS version, Handbook of Chemistry and Physics,75^(th) Ed. Additionally, general principles of organic chemistry aredescribed in “Organic Chemistry”, Thomas Sorrell, University ScienceBooks, Sausalito: 1999, and “March's Advanced Organic Chemistry”, 5^(th)Ed., Ed.: Smith, M. B. and March, J., John Wiley & Sons, New York: 2001,the entire contents of which are hereby incorporated by reference.

The term “aliphatic” or “aliphatic group,” as used herein, means astraight-chain (i.e., unbranched) or branched, substituted orunsubstituted hydrocarbon chain that is completely saturated or thatcontains one or more units of unsaturation, or a monocyclic hydrocarbonor bicyclic hydrocarbon that is completely saturated or that containsone or more units of unsaturation, but which is not aromatic (alsoreferred to herein as “carbocycle,” “cycloaliphatic” or “cycloalkyl”),that has a single point of attachment to the rest of the molecule.Unless otherwise specified, aliphatic groups contain 1-6 aliphaticcarbon atoms. In some embodiments, aliphatic groups contain 1-5aliphatic carbon atoms. In other embodiments, aliphatic groups contain1-4 aliphatic carbon atoms. In still other embodiments, aliphatic groupscontain 1-3 aliphatic carbon atoms, and in yet other embodiments,aliphatic groups contain 1-2 aliphatic carbon atoms. In someembodiments, “cycloaliphatic” (or “carbocycle” or “cycloalkyl”) refersto a monocyclic C₃-C₆ hydrocarbon that is completely saturated or thatcontains one or more units of unsaturation, but which is not aromatic,that has a single point of attachment to the rest of the molecule.Suitable aliphatic groups include, but are not limited to, linear orbranched, substituted or unsubstituted alkyl, alkenyl, alkynyl groupsand hybrids thereof such as (cycloalkyl)alkyl, (cycloalkenyl)alkyl or(cycloalkyl)alkenyl.

As used herein, the term “bridged bicyclic” refers to any bicyclic ringsystem, i.e. carbocyclic or heterocyclic, saturated or partiallyunsaturated, having at least one bridge. As defined by IUPAC, a “bridge”is an unbranched chain of atoms or an atom or a valence bond connectingtwo bridgeheads, where a “bridgehead” is any skeletal atom of the ringsystem which is bonded to three or more skeletal atoms (excludinghydrogen). In some embodiments, a bridged bicyclic group has 7-12 ringmembers and 0-4 heteroatoms independently selected from nitrogen,oxygen, or sulfur. Such bridged bicyclic groups are well known in theart and include those groups set forth below where each group isattached to the rest of the molecule at any substitutable carbon ornitrogen atom. Unless otherwise specified, a bridged bicyclic group isoptionally substituted with one or more substituents as set forth foraliphatic groups. Additionally or alternatively, any substitutablenitrogen of a bridged bicyclic group is optionally substituted.Exemplary bridged bicyclics include:

The term “lower alkyl” refers to a C₁₋₄ straight or branched alkylgroup. Exemplary lower alkyl groups are methyl, ethyl, propyl,isopropyl, butyl, isobutyl, and tert-butyl.

The term “lower haloalkyl” refers to a C₁₋₄ straight or branched alkylgroup that is substituted with one or more halogen atoms.

The term “heteroatom” means one or more of oxygen, sulfur, nitrogen,phosphorus, or silicon (including, any oxidized form of nitrogen,sulfur, phosphorus, or silicon; the quaternized form of any basicnitrogen or; a substitutable nitrogen of a heterocyclic ring, forexample N (as in 3,4-dihydro-2H-pyrrolyl), NH (as in pyrrolidinyl) orNR⁻ (as in N-substituted pyrrolidinyl)).

The term “unsaturated”, as used herein, means that a moiety has one ormore units of unsaturation.

As used herein, the term “bivalent C₁₋₈ (or C₁₋₆) saturated orunsaturated, straight or branched, hydrocarbon chain,” refers tobivalent alkylene, alkenylene, and alkynylene chains that are straightor branched as defined herein.

The term “alkylene” refers to a bivalent alkyl group. An “alkylenechain” is a polymethylene group, i.e., —(CH₂)_(n)—, wherein n is apositive integer, preferably from 1 to 6, from 1 to 4, from 1 to 3, from1 to 2, or from 2 to 3. A substituted alkylene chain is a polymethylenegroup in which one or more methylene hydrogen atoms are replaced with asubstituent. Suitable substituents include those described below for asubstituted aliphatic group.

The term “alkenylene” refers to a bivalent alkenyl group. A substitutedalkenylene chain is a polymethylene group containing at least one doublebond in which one or more hydrogen atoms are replaced with asubstituent. Suitable substituents include those described below for asubstituted aliphatic group.

The term “halogen” means F, Cl, Br, or I.

The term “aryl” used alone or as part of a larger moiety as in“aralkyl,” “aralkoxy,” or “aryloxyalkyl,” refers to monocyclic orbicyclic ring systems having a total of five to fourteen ring members,wherein at least one ring in the system is aromatic and wherein eachring in the system contains 3 to 7 ring members. The term “aryl” may beused interchangeably with the term “aryl ring.” In certain embodimentsof the present invention, “aryl” refers to an aromatic ring system whichincludes, but not limited to, phenyl, biphenyl, naphthyl, anthracyl andthe like, which may bear one or more substituents. Also included withinthe scope of the term “aryl,” as it is used herein, is a group in whichan aromatic ring is fused to one or more non-aromatic rings, such asindanyl, phthalimidyl, naphthimidyl, phenanthridinyl, ortetrahydronaphthyl, and the like.

The terms “heteroaryl” and “heteroar—,” used alone or as part of alarger moiety, e.g., “heteroaralkyl,” or “heteroaralkoxy,” refer togroups having 5 to 10 ring atoms, preferably 5, 6, or 9 ring atoms;having 6, 10, or 14 π electrons shared in a cyclic array; and having, inaddition to carbon atoms, from one to five heteroatoms. The term“heteroatom” refers to nitrogen, oxygen, or sulfur, and includes anyoxidized form of nitrogen or sulfur, and any quaternized form of a basicnitrogen. Heteroaryl groups include, without limitation, thienyl,furanyl, pyrrolyl, imidazolyl, pyrazolyl, triazolyl, tetrazolyl,oxazolyl, isoxazolyl, oxadiazolyl, thiazolyl, isothiazolyl,thiadiazolyl, pyridyl, pyridazinyl, pyrimidinyl, pyrazinyl, indolizinyl,purinyl, naphthyridinyl, and pteridinyl. The terms “heteroaryl” and“heteroar-”, as used herein, also include groups in which aheteroaromatic ring is fused to one or more aryl, cycloaliphatic, orheterocyclyl rings, where the radical or point of attachment is on theheteroaromatic ring. Nonlimiting examples include indolyl, isoindolyl,benzothienyl, benzofuranyl, dibenzofuranyl, indazolyl, benzimidazolyl,benzthiazolyl, quinolyl, isoquinolyl, cinnolinyl, phthalazinyl,quinazolinyl, quinoxalinyl, 4H-quinolizinyl, carbazolyl, acridinyl,phenazinyl, phenothiazinyl, phenoxazinyl, tetrahydroquinolinyl,tetrahydroisoquinolinyl, and pyrido[2,3-b]-1,4-oxazin-3(4H)-one. Aheteroaryl group may be mono- or bicyclic. The term “heteroaryl” may beused interchangeably with the terms “heteroaryl ring,” “heteroarylgroup,” or “heteroaromatic,” any of which terms include rings that areoptionally substituted. The term “heteroaralkyl” refers to an alkylgroup substituted with a heteroaryl, wherein the alkyl and heteroarylportions independently are optionally substituted.

As used herein, the terms “heterocycle,” “heterocyclyl,” “heterocyclicradical,” and “heterocyclic ring” are used interchangeably and refer toa stable 5- to 7-membered monocyclic or 7-10-membered bicyclicheterocyclic moiety that is either saturated or partially unsaturated,and having, in addition to carbon atoms, one or more, preferably one tofour, heteroatoms, as defined above. When used in reference to a ringatom of a heterocycle, the term “nitrogen” includes a substitutednitrogen. As an example, in a saturated or partially unsaturated ringhaving 0-3 heteroatoms selected from oxygen, sulfur or nitrogen, thenitrogen may be N (as in 3,4-dihydro-2H-pyrrolyl), NH (as inpyrrolidinyl), or ⁺NR (as in N-substituted pyrrolidinyl).

A heterocyclic ring can be attached to its pendant group at anyheteroatom or carbon atom that results in a stable structure and any ofthe ring atoms can be optionally substituted. Examples of such saturatedor partially unsaturated heterocyclic radicals include, withoutlimitation, tetrahydrofuranyl, tetrahydrothiophenyl, pyrrolidinyl,piperidinyl, pyrrolinyl, tetrahydroquinolinyl, tetrahydroisoquinolinyl,decahydroquinolinyl, oxazolidinyl, piperazinyl, dioxanyl, dioxolanyl, diazepinyl, oxazepinyl, thiazepinyl, morpholinyl, and quinuclidinyl. Theterms “heterocycle,” “heterocyclyl,” “heterocyclyl ring,” “heterocyclicgroup,” “heterocyclic moiety,” and “heterocyclic radical,” are usedinterchangeably herein, and also include groups in which a heterocyclylring is fused to one or more aryl, heteroaryl, or cycloaliphatic rings,such as indolinyl, 3H-indolyl, chromanyl, phenanthridinyl, ortetrahydroquinolinyl. A heterocyclyl group may be mono- or bicyclic. Theterm “heterocyclylalkyl” refers to an alkyl group substituted with aheterocyclyl, wherein the alkyl and heterocyclyl portions independentlyare optionally substituted.

As used herein, the term “partially unsaturated” refers to a ring moietythat includes at least one double or triple bond. The term “partiallyunsaturated” is intended to encompass rings having multiple sites ofunsaturation, but is not intended to include aryl or heteroarylmoieties, as herein defined.

As described herein, compounds of the invention may contain “optionallysubstituted” moieties. In general, the term “substituted,” whetherpreceded by the term “optionally” or not, means that one or morehydrogens of the designated moiety are replaced with a suitablesubstituent. Unless otherwise indicated, an “optionally substituted”group may have a suitable substituent (“optional substituent”) at eachsubstitutable position of the group, and when more than one position inany given structure may be substituted with more than one substituentselected from a specified group, the substituent may be either the sameor different at every position. Combinations of substituents envisionedby this invention are preferably those that result in the formation ofstable or chemically feasible compounds. The term “stable,” as usedherein, refers to compounds that are not substantially altered whensubjected to conditions to allow for their production, detection, and,in certain embodiments, their recovery, purification, and use for one ormore of the purposes disclosed herein.

Suitable monovalent substituents on a substitutable carbon atom of an“optionally substituted” group are independently halogen;—(CH₂)₀₋₄R^(o); —(CH₂)₀₋₄OR^(o); —O(CH₂)₀₋₄R^(o); —O—(CH₂)₀₋₄C(O)OR^(o);—(CH₂)₀₋₄CH(OR^(o))₂; —(CH₂)₀₋₄SR^(o); —(CH₂)₀₋₄Ph, which may besubstituted with R^(o); —(CH₂)₀₋₄O(CH₂)₀₋₁Ph which may be substitutedwith R^(o); —CH═CHPh, which may be substituted with R^(o);—(CH₂)₀₋₄O(CH₂)₀₋₁ pyridyl which may be substituted with R^(o); —NO₂;—CN; —N₃; —(CH₂)₀₋₄N(R^(o))₂; —(CH₂)₀₋₄N(R^(o))C(O)R^(o);—N(R^(o))C(S)R^(o); —(CH₂)₀₋₄N(R^(o))C(O)NR^(o) ₂; —N(R^(o))C(S)NR^(o)₂; —(CH₂)₀₋₄N(R^(o))C(O)OR^(o); —N(R^(o))N(R^(o))C(O)OR^(o);—N(R^(o))N(R^(o))C(O)NR^(o) ₂; —N(R^(o))N(R^(o))C(O)OR^(o);—(CH₂)₀₋₄C(O)R^(o); —C(S)R^(o); —(CH₂)₀₋₄C(O)OR^(o);—(CH₂)₀₋₄C(O)SR^(o); —(CH₂)₀₋₄C(O)OSiR^(o) ₃; —(CH₂)₀₋₄OC(O)R^(o);—OC(O)(CH₂)₀₋₄SR—, SC(S)SR^(o); —(CH₂)₀₋₄SC(O)R^(o); —(CH₂)₀₋₄C(O)NR^(o)₂; —C(S)NR^(o) ₂; —C(S)SR^(o); —SC(S)SR^(o); —(CH₂)₀₋₄OC(O)NR^(o) ₂;—C(O)N(OR^(o))R^(o); —C(O)C(O)R^(o); —C(O)CH₂C(O)R^(o);—C(NOR^(o))R^(o); —(CH₂)₀₋₄SSR^(o); —(CH₂)₀₋₄S(O)₂R^(o);—(CH₂)₀₋₄S(O)₂OR^(o); —(CH₂)₀₋₄OS(O)₂R^(o); —S(O)₂NR^(o) ₂;—(CH₂)₀₋₄S(O)R^(o); —N(R^(o))S(O)₂NR^(o) ₂; —N(R^(o))S(O)₂OR^(o);—N(OR^(o))R^(o); —C(NH)NR^(o) ₂; —P(O)₂R^(o); —P(O)R^(o) ₂; —OP(O)R^(o)₂; —OP(O)(OR^(o))₂; SiR^(o) ₃; —(C₁₋₄ straight or branchedalkylene)O—N(R^(o))₂, or —(C₁₋₄ straight or branchedalkylene)C(O)O—N(R^(o))₂, wherein each R^(o) may be substituted asdefined below and is independently hydrogen, C₁₋₆ aliphatic, —CH₂PH,—O(CH₂)₀₋₁Ph, —CH₂—(5-6 membered heteroaryl ring), or a 5-6-memberedsaturated, partially unsaturated, or aryl ring having 0-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur, or,notwithstanding the definition above, two independent occurrences ofR^(o), taken together with their intervening atom(s), form a3-12-membered saturated, partially unsaturated, or aryl mono- orbicyclic ring having 0-4 heteroatoms independently selected fromnitrogen, oxygen, or sulfur, which may be substituted as defined below.

Suitable monovalent substituents on R^(o) (or the ring formed by takingtwo independent occurrences of R^(o) together with their interveningatoms), are independently halogen, —(CH₂)₀₋₂R^(⋅), -(haloR^(⋅)),—(CH₂)₀₋₂OH, —(CH₂)₀₋₂OR^(⋅), —(CH₂)₀₋₂CH(OR^(⋅))₂; —O(haloR^(⋅)), —CN,—N₃, —(CH₂)₀₋₂C(O)R^(⋅), —(CH₂)₀₋₂C(O)OH, —(CH₂)₀₋₂C(O)OR^(⋅),—(CH₂)₀₋₂SR^(⋅), —(CH₂)₀₋₂SH, —(CH₂)₀₋₂NH₂, —(CH₂)₀₋₂NHR^(⋅),—(CH₂)₀₋₂NR^(⋅) ₂, —NO₂, —SiR^(⋅) ₃, —OSiR^(⋅) ₃, —C(O)SR^(⋅), —(C₁₋₄straight or branched alkylene)C(O)OR^(⋅), or —SSR^(⋅) wherein each R^(⋅)is unsubstituted or where preceded by “halo” is substituted only withone or more halogens, and is independently selected from C₁₋₄ aliphatic,—CH₂Ph, —O(CH₂)₀₋₁Ph, or a 5-6-membered saturated, partiallyunsaturated, or aryl ring having 0-4 heteroatoms independently selectedfrom nitrogen, oxygen, or sulfur. Suitable divalent substituents on asaturated carbon atom of R^(o) include ═O and ═S.

Suitable divalent substituents on a saturated carbon atom of an“optionally substituted” group include the following: ═O, ═S, ═NNR^(*)₂, ═NNHC(O)R^(*), ═NNHC(O)OR^(*), ═NNHS(O)₂R^(*), ═NR⁸, ═NOR⁸, —O(C(R⁸₂))₂₋₃O—, or —S(C(R⁸ ₂))₂₋₃S—, wherein each independent occurrence ofR^(*) is selected from hydrogen, C₁₋₆ aliphatic which may be substitutedas defined below, or an unsubstituted 5-6-membered saturated, partiallyunsaturated, or aryl ring having 0-4 heteroatoms independently selectedfrom nitrogen, oxygen, or sulfur. Suitable divalent substituents thatare bound to vicinal substitutable carbons of an “optionallysubstituted” group include: —O(CR⁸ ₂)₂₋₃O—, wherein each independentoccurrence of R^(*) is selected from hydrogen, C₁₋₆ aliphatic which maybe substituted as defined below, or an unsubstituted 5-6-memberedsaturated, partially unsaturated, or aryl ring having 0-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur.

Suitable substituents on the aliphatic group of R^(*) include halogen,—R^(⋅), -(haloR^(⋅)), —OH, —OR^(⋅), —O(haloR^(⋅)), —CN, —C(O)OH,—C(O)OR^(⋅), —NH₂, —NHR^(⋅), —NR^(⋅) ₂, or —NO₂, wherein each R^(⋅)isunsubstituted or where preceded by “halo” is substituted only with oneor more halogens, and is independently C₁₋₄ aliphatic, —CH₂Ph,—O(CH₂)₀₋₁Ph, or a 5-6-membered saturated, partially unsaturated, oraryl ring having 0-4 heteroatoms independently selected from nitrogen,oxygen, or sulfur.

Suitable substituents on a substitutable nitrogen of an “optionallysubstituted” group include —R^(†), —NR^(†) ₂, —C(O)R^(†), —C(O)OR^(†),—C(O)C(O)R^(†), —C(O)CH₂C(O)R^(†), —S(O)₂R^(†), —S(O)₂NR^(†) ₂,—C(S)NR⁵⁵⁴ ₂, —C(NH)NR^(†) ₂, or —N(R^(†))S(O)₂,R^(†); wherein eachR^(†)is independently hydrogen, C₁₋₆ aliphatic which may be substitutedas defined below, unsubstituted —OPh, or an unsubstituted 5-6-memberedsaturated, partially unsaturated, or aryl ring having 0-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur, or,notwithstanding the definition above, two independent occurrences ofR^(†), taken together with their intervening atom(s) form anunsubstituted 3-12-membered saturated, partially unsaturated, or arylmono- or bicyclic ring having 0-4 heteroatoms independently selectedfrom nitrogen, oxygen, or sulfur.

Suitable substituents on the aliphatic group of R^(†) are independentlyhalogen, —R^(⋅), -(haloR^(⋅)), —OH, —OR^(⋅), —O(haloR^(⋅)), —CN,—C(O)OH, —C(O)OR^(⋅), —NH₂, —NHR^(⋅), —NR^(⋅) ₂, or —NO₂, wherein eachR^(⋅) is unsubstituted or where preceded by “halo” is substituted onlywith one or more halogens, and is independently C₁₋₄ aliphatic, —CH₂Ph,—O(CH₂)₀₋₁Ph, or a 5-6-membered saturated, partially unsaturated, oraryl ring having 0-4 heteroatoms independently selected from nitrogen,oxygen, or sulfur.

As used herein, the term “pharmaceutically acceptable salt” refers tothose salts which are, within the scope of sound medical judgment,suitable for use in contact with the tissues of humans and lower animalswithout undue toxicity, irritation, allergic response and the like, andare commensurate with a reasonable benefit/risk ratio. Pharmaceuticallyacceptable salts are well known in the art. For example, S. M. Berge etal., describe pharmaceutically acceptable salts in detail in J.Pharmaceutical Sciences, 1977, 66, 1-19, incorporated herein byreference. Pharmaceutically acceptable salts of the compounds of thisinvention include those derived from suitable inorganic and organicacids and bases. Examples of pharmaceutically acceptable, nontoxic acidaddition salts are salts of an amino group formed with inorganic acidssuch as hydrochloric acid, hydrobromic acid, phosphoric acid, sulfuricacid and perchloric acid or with organic acids such as acetic acid,oxalic acid, maleic acid, tartaric acid, citric acid, succinic acid ormalonic acid or by using other methods used in the art such as ionexchange. Other pharmaceutically acceptable salts include adipate,alginate, ascorbate, aspartate, benzenesulfonate, benzoate, bisulfate,borate, butyrate, camphorate, camphorsulfonate, citrate,cyclopentanepropionate, digluconate, dodecylsulfate, ethanesulfonate,formate, fumarate, glucoheptonate, glycerophosphate, gluconate,hemisulfate, heptanoate, hexanoate, hydroiodide,2-hydroxy-ethanesulfonate, lactobionate, lactate, laurate, laurylsulfate, malate, maleate, malonate, methanesulfonate,2-naphthalenesulfonate, nicotinate, nitrate, oleate, oxalate, palmitate,pamoate, pectinate, persulfate, 3-phenylpropionate, phosphate, pivalate,propionate, stearate, succinate, sulfate, tartrate, thiocyanate,p-toluenesulfonate, undecanoate, valerate salts, and the like.

Salts derived from appropriate bases include alkali metal, alkalineearth metal, ammonium and N⁺(C₁₋₄alkyl)₄ salts. Representative alkali oralkaline earth metal salts include sodium, lithium, potassium, calcium,magnesium, and the like. Further pharmaceutically acceptable saltsinclude, when appropriate, nontoxic ammonium, quaternary ammonium, andamine cations formed using counterions such as halide, hydroxide,carboxylate, sulfate, phosphate, nitrate, loweralkyl sulfonate and arylsulfonate.

Unless otherwise stated, structures depicted herein are also meant toinclude all isomeric (e.g., enantiomeric, diastereomeric, and geometric(or conformational)) forms of the structure; for example, the R and Sconfigurations for each asymmetric center, Z and E double bond isomers,and Z and E conformational isomers. Therefore, single stereochemicalisomers as well as enantiomeric, diastereomeric, and geometric (orconformational) mixtures of the present compounds are within the scopeof the invention. Unless otherwise stated, all tautomeric forms of thecompounds of the invention are within the scope of the invention.Additionally, unless otherwise stated, structures depicted herein arealso meant to include compounds that differ only in the presence of oneor more isotopically enriched atoms. For example, compounds having thepresent structures including the replacement of hydrogen by deuterium ortritium, or the replacement of a carbon by a ¹³C- or ¹⁴C-enriched carbonare within the scope of this invention. Such compounds are useful, forexample, as analytical tools, as probes in biological assays, or astherapeutic agents in accordance with the present invention. In certainembodiments, a warhead moiety, R¹, of a provided compound comprises oneor more deuterium atoms.

As used herein, the term “inhibitor” is defined as a compound that bindsto and/or modulates or inhibits a target RNA with measurable affinity.In certain embodiments, an inhibitor has an IC₅₀ and/or binding constantof less than about 100 μM, less than about 50 μM, less than about 1 μM,less than about 500 nM, less than about 100 nM, less than about 10 nM,or less than about 1 nM.

The terms “measurable affinity” and “measurably inhibit,” as usedherein, mean a measurable change in a downstream biological effectbetween a sample comprising a compound of the present invention, orcomposition thereof, and a target RNA, and an equivalent samplecomprising the target RNA, in the absence of said compound, orcomposition thereof

The term “RNA” (ribonucleic acid) as used herein, meansnaturally-occurring or synthetic oligoribonucleotides independent ofsource (e.g., the RNA may be produced by a human, animal, plant, virus,or bacterium, or may be synthetic in origin), biological context (e.g.,the RNA may be in the nucleus, circulating in the blood, in vitro, celllysate, or isolated or pure form), or physical form (e.g., the RNA maybe in single-, double-, or triple-stranded form (including RNA-DNAhybrids), may include epigenetic modifications, nativepost-transcriptional modifications, artificial modifications (e.g.,obtained by chemical or in vitro modification), or other modifications,may be bound to, e.g., metal ions, small molecules, protein chaperones,or co-factors, or may be in a denatured, partially denatured, or foldedstate including any native or unnatural secondary or tertiary structuresuch as junctions (e.g., cis or trans three-way junctions (3WJ)),quadruplexes, hairpins, triplexes, hairpins, bulge loops, pseudoknots,and internal loops, etc., and any transient forms or structures adoptedby the RNA). In some embodiments, the RNA is 100 or more nucleotides inlength. In some embodiments, the RNA is 250 or more nucleotides inlength. In some embodiments, the RNA is 350, 450, 500, 600, 750, or1,000, 2,000, 3,000, 4,000, 5,000, 7,500, 10,000, 15,000, 25,000,50,000, or more nucleotides in length. In some embodiments, the RNA isbetween 250 and 1,000 nucleotides in length. In some embodiments, theRNA is a pre-RNA, pre-miRNA, or pretranscript. In some embodiments, theRNA is a non-coding RNA (ncRNA), messenger RNA (mRNA), micro-RNA(miRNA), a ribozyme, riboswitch, lncRNA, lincRNA, snoRNA, snRNA, scaRNA,piRNA, ceRNA, pseudo-gene, viral RNA, or bacterial RNA. The term “targetRNA,” as used herein, means any type of RNA having a secondary ortertiary structure capable of binding a small molecule ligand describedherein. The target RNA may be inside a cell, in a cell lysate, or inisolated form prior to contacting the compound.

Photoactivatable Groups

Suitable covalent modifier moieties (e.g. R^(mod) shown in FormulaeI-VIII above) for use in the present invention generally includephotoactivatable groups that generate a reactive intermediate uponirradiation with visible or ultraviolet light. In some embodiments, thephotoactivatable group is a functional group that generates a carbon- oroxygen-centered radical, an aryl or heteroaryl carbocation, a nitrene,or a carbene intermediate upon irradiation with ultraviolet (UV)radiation; and wherein R^(mod) is capable of reacting with a target RNAto which Ligand binds to produce a covalent bond with the target RNA.Exemplary photoactivatable chromophores and the reactive speciesgenerated after irradiation are shown below.

Since the warhead is unreactive prior to activation, a non-covalentRNA-ligand interaction is required for successful photoactivatedmodification. The reactive carbene/nitrene intermediates are rapidlyquenched by water if a suitably positioned macromolecule is not present.

α-pyrones and pyrimidones are also photoactivatable groups that may beused in the present invention. For example, Battenberg, O. A. et al. (J.Org. Chem. 2011, 76, 6075-6087) disclose photoprobes such as thefollowing:

In some embodiments, the photoactivatable group is selected from apyrone or pyrimidone such as those above.

In other embodiments, the photoactivable group, after irradiation andformation of a covalent bond with the target RNA, undergoes anequilibrium process that optionally includes reversion to its originalstate. Synthetic molecules that are isomerizable in a reversible fashionunder light irradiation of different wavelengths and which may be usedas photoactivatable groups include diazobenzenes, dihydropyrenes,spirooxazines, anthracenes, fulgides, and spiropyrans. An exemplaryspiropyran and its irradiation-induced equilibrium process are shown inthe scheme below.

wherein R═—(CH₂)₂O₂C(CH₂)₂NH₂ and 1 above may be optionally substituted;the spiropyran may be linked to a small molecule ligand and optionalpull-down group by a covalent bond or tether as described herein. Onecharacteristic of spiropyran 1 in comparison with other reversiblesystems lies in its photochemical switching being virtually complete(>95% of 2a after UV irradiation at 365 nm) because of the distinctivelydifferent absorption maxima of 1 (350 nm) and 2a (563 nm), unlikediazobenzenes, which reach a photostationary state of 70-90% cis whenexposed to UV light of 365 nm. The equilibrium of 2a and 2b can also beinfluenced by pH. See, e.g., Young, D. D. et al., ChemBioChem 2008, 9,1225-1228.

In some embodiments, the photoactivatable group is selected from anoptionally substituted phenyl or 8-10 membered bicyclic aromaticcarbocyclic azide or 5-8 membered heteroaryl or 8-10 membered bicyclicheteroaryl azide, optionally substituted benzoyl azide or 5-8 memberedheteroaroyl azide or 8-10 membered heteroaroyl azide wherein 1-3 atomsof the ring atoms are selected from nitrogen, sulfur, or oxygen,optionally substituted phenyl or 8-10 membered bicyclic aromaticcarbocyclic diazonium salt, optionally substituted 5-8 memberedheteroaryl or 8-10 membered bicyclic heteroaryl diazonium salt wherein1-3 atoms of the ring atoms are selected from nitrogen, sulfur, oroxygen, optionally substituted C₂₋₆ aliphatic diazo functional group,optionally substituted C₂₋₆ aliphatic diazirine, or optionallysubstituted diphenyl or 8-10-membered diheteroaryl ketone wherein 1-3atoms of the ring atoms are selected from nitrogen, sulfur, or oxygen,optionally substituted dihydropyrene, optionally substitutedspirooxazine, optionally substituted anthracene, optionally substitutedfulgide, optionally substituted spiropyran, optionally substituteda-pyrone or optionally substituted pyrimidone.

In some embodiments, the photoactivatable group is selected from, e.g.

Photoactivatable groups can be conjugated to small molecule ligands ortethers by conventional coupling reactions known to those of ordinaryskill in the art and as described herein. For example, photoactivatableamino acids such as D- or L-photoleucine, photomethionine, photolysine,para-benzoylphenylalanine, and others can serve as convenient means ofintroducing a photoactivatable group into a compound in accordance withthe present invention.

In some embodiments, the photoactivatable group is an aroyl orheteroaroyl azide, such as nicotinoyl azide (NAz). Such compounds formnitrene intermediates upon irradiation, and have been used to studysolvent accessibility of nucleic acids such as the SAM-1 riboswitch andrRNA in cells. NAz probes react, for example, with the C8 position ofaccessible purines.

The term “covalent modifier moiety” or “warhead” as used herein, meansany photoactivatable group capable of forming a covalent bond with anavailable nucleotide of a RNA to produce a modified RNA (such as aC8-modified purine or 2′-O—modified RNA) after irradiation with visibleor UV light.

The wavelength of visible or UV light for activating thephotoactivatable group is generally selected to generate the reactiveintermediate such as a nitrene without substantially degrading thebiological system under investigation or causing off-target reactivity.The wavelength is generally a wavelength known to function to generatethe reactive intermediate for each specific protoactivatable group. Insome embodiments, the wavelenegth is about 252 nm, 302 nm, or 365 nm; or254 nm, 265-275 nm, 365 nm, 300-460 nm, or about 250 nm to about 350 nm.

When an aryl azide is exposed to UV light (250 to 350 nm), it forms anitrene group that can initiate addition reactions with double bonds,insertion into C—H and N—H sites, or subsequent ring expansion to reactwith a nucleophile (e.g., primary amines). The latter reaction pathdominates when primary amines are present in the sample.

Thiol-containing reducing agents (e.g., DTT or2-mercaptoethanol) must beavoided in the sample solution during all steps before and duringphoto-activation, because they reduce the azide functional group to anamine, preventing photo-activation. Reactions can be performed in avariety of amine-free buffer conditions. If working withheterobifunctional photoreactive crosslinkers, use buffers compatiblewith both reactive chemistries involved. In general, experiments areperformed in subdued light and/or with reaction vessels covered in foiluntil photoreaction is intended. Typically, photo-activation isaccomplished with a hand-held UV lamp positioned close to the reactionsolution and shining directly on it (i.e., not through glass orpolypropylene) for several minutes.

Examples of aryl azides include simple phenyl azides, hydroxyphenylazides, and nitrophenyl azides. Generally, short-wavelength UV light(e.g., 254 nm; 265 to 275 nm) is needed to efficiently activate simplephenyl azides, while long-UV light (e.g, 365 nm; 300 to 460 nm) issufficient for nitrophenyl azides.

Covalent Modification of RBP Proteins and Other Proximate Biomolecules

In some embodiments, the photoactivatable group reacts with a protein inproximity to the small molecule ligand binding site on a target RNA. RNAbinding proteins (RBPs) are frequently associated with target RNAs ofinterest. In some cases, a RBP is associated with or otherwise inproximity to the targeted RNA sub-structure to which a disclosedphotoactivatable compound binds. Accordingly, an advantage of thephotoaffinity warheads is that they are agnostic about covalentmodification of RNAs or proteins such as RBPs proximal to thephotoactivatable group that is attached to the small molecule ligand.Thus, in some embodiments, a disclosed compound covalently modifieseither a target RNA or a RBP associated with the target RNA. This inturn yields insight into which RBPs are bound to a target RNA and inwhich cells or tissues of an organism, as well as the effect of thesmall molecule binding on RBP binding.

Thus, in one aspect, the present invention provides a method ofdetermining the presence of or association/binding of a RNA bindingprotein (RBP) with a target RNA, comprising the step of contacting thetarget RNA with a disclosed compound and irradiating the compound withvisible or UV light, and optionally performing one or more assays todetermine whether a RBP has been covalently modified by thephotoactivatable group of the compound.

The highly reactive and thus relatively indiscriminate carbenes,nitrenes, diradicals, and other intermediates produced by activation ofthe photoaffinity warheads thus have the advantage of covalentlymodifying a target RNA or any biomolecule in proximity, unlikepreviously known methods.

Tethering Groups (Linkers)

The present invention contemplates the use of a wide variety oftethering groups (tethers; e.g., variables T¹ and T² as shown inFormulae I-VIII above) to provide optimal binding and reactivity towardnucleotides or RBPs proximal to the binding site of a target RNA. Insome embodiments, T¹ and T² are selected from those shown in FIGS.10-17. For example, in some embodiments, T¹ and/or T² is a polyethyleneglycol (PEG) group of, e.g., 1-10 ethylene glycol subunits. In someembodiments, T¹ and/or T² is an optionally substituted C₁₋₁₂ aliphaticgroup or a peptide comprising 1-8 amino acids.

In some embodiments, T¹ and T² are each independently selected from L¹or L², as L¹ and L² are defined in embodiments herein.

In some embodiments, the physical properties such as the length,rigidity, hydrophobicity, and/or other properties of the tether areselected to optimize the pattern of proximity-induced covalent bondformation between the target RNA or an associated RBP and thephotoactivatable group (warhead). In some embodiments, the physicalproperties of the tether (such as those above) are selected so that,upon binding of the compound to the active or allosteric sites of atarget RNA, the modifying moiety selectively reacts with a an availablefunctionality of the target RNA such as a purine C8 carbon or 2′—OHgroup of the target RNA proximal to the active site or allosteric sites,or reacts with a proximal amino acid of a RBP.

Click-Ready Groups

A variety of bioorthogonal reaction partners (e.g., R^(CG) in FormulaeI-VIII or R² in Formulae above) may be used in the present invention tocouple a compound described herein with a pull-down moiety. The term“bioorthogonal chemistry” or “bioorthogonal reaction,” as used herein,refers to any chemical reaction that can take place in living systemswithout interfering with native biochemical processes. Accordingly, a“bioorthogonal reaction partner” is a chemical moiety capable ofundergoing a bioorthogonal reaction with an appropriate reaction partnerto couple a compound described herein to a pull-down moiety. In someembodiments, a bioorthogonal reaction partner is covalently attached tothe chemical modifying moiety or the tethering group. In someembodiments, the bioorthogonal reaction partner is selected from aclick-ready group or a group capable of undergoing a nitrone/cyclooctynereaction, oxime/hydrazone formation, a tetrazine ligation, anisocyanide-based click reaction, or a quadricyclane ligation.

In some embodiments, the bioorthogonal reaction partner is a click-readygroup. The term “click-ready group” refers to a chemical moiety capableof undergoing a click reaction, such as an azide or alkyne.

Click reactions tend to involve high-energy (“spring-loaded”) reagentswith well-defined reaction coordinates, that give rise to selectivebond-forming events of wide scope. Examples include nucleophilictrapping of strained-ring electrophiles (epoxide, aziridines,aziridinium ions, episulfonium ions), certain carbonyl reactivity (e.g.,the reaction between aldehydes and hydrazines or hydroxylamines), andseveral cycloaddition reactions. The azide-alkyne 1,3-dipolarcycloaddition and the Diels-Alder cycloaddition are two such reactions.

Such click reactions (i.e., dipolar cycloadditions) are associated witha high activation energy and therefore require heat or a catalyst.Indeed, use of a copper catalyst is routinely employed in clickreactions. However, in certain instances where click chemistry isparticularly useful (e.g., in bioconjugation reactions), the presence ofcopper can be detrimental (See Wolbers, F. et al.; Electrophoresis 2006,27, 5073). Accordingly, methods of performing dipolar cycloadditionreactions were developed without the use of metal catalysis. Such “metalfree” click reactions utilize activated moieties in order to facilitatecycloaddition. Therefore, the present invention provides click-readygroups suitable for metal-free click chemistry.

Certain metal-free click moieties are known in the literature. Examplesinclude 4-dibenzocyclooctynol (DIBO) (from Ning et al; Angew Chem IntEd, 2008, 47, 2253); gem-difluorinated cyclooctynes (DIFO or DFO) (fromCodelli, et al.; J. Am. Chem. Soc. 2008, 130, 11486-11493.);biarylazacyclooctynone (BARAC) (from Jewett et al.; J. Am. Chem. Soc.2010, 132, 3688.); or bicyclononyne (BCN) (From Dommerholt, et al.;Angew Chem Int Ed, 2010, 49, 9422-9425).

As used herein, the phrase “a moiety suitable for metal-free clickchemistry” refers to a functional group capable of dipolar cycloadditionwithout use of a metal catalyst. Such moieties include an activatedalkyne (such as a strained cyclooctyne), an oxime (such as a nitrileoxide precursor), or oxanorbornadiene, for coupling to an azide to forma cycloaddition product (e.g., triazole or isoxazole).

Thus, in certain embodiments, the click-ready group is selected from anazide, an alkyne, 4-dibenzocyclooctynol (DIEM) gem-difluorinatedcyclooctynes (DIFO or DFO), biarylazacyclooctynone (BARAC),bicyclononyne (BCN), a strained cyclooctyne, an oxime, oroxanorbornadiene.

In some embodiments, the click-ready group is selected from those shownin FIG. 9.

Pull-down Groups

A number of pull-down groups (R^(PD) in, for example, Formulae I-VIIIabove) may be used in the present invention. In some embodiments,pull-down groups contain a bioorthogonal reaction partner that reactswith a click-ready group to attach the pull-down group to the rest ofthe compound, as well as an appropriate functional group or affinitygroup such as a hapten (e.g., biotin) or a radiolabel allowing forselective isolation or detection of the pulled-down compound. Forexample, use of avidin or streptavidin to interact with a pull-downgroup would allow isolation of only those RNAs that had been covalentlymodified, as explained in further detail below.

In some embodiments, a pull-down group is covalently attached to adisclosed compound as described above and in formulae described herein,before binding to a target RNA and before irradiation to activate thephotoactivatable group. In other embodiments, a pull-down group isattached to a compound or RNA conjugate after the photoactivatable grouphas been irradiated and covalent modification of a target RNA has takenplace. In some embodiments, such attachment is achieved by abioorthogoal reaction between a click-ready group on the compound or RNAconjugate and an appropriate reaction partner that is part of thepull-down group. Accordingly, in some embodiments, the pull-down groupcomprises a click-ready group attached via a tether (as describedelsewhere herein) to an affinity group or bioorthogonal functionalgroup. In some embodiments, the affinity group or bioorthogonalfunctional group is a hapten (e.g., biotin) or a radiolabel such as¹²⁵I, ¹⁴C, ³²P, or ³H.

3. General Methods of Providing the Present Compounds

The compounds of this invention may be prepared or isolated in generalby synthetic and/or semi-synthetic methods known to those skilled in theart for analogous compounds and by methods described in detail in theExamples and Figures, herein.

In the schemes and chemical reactions depicted in the detaileddescription, Examples, and Figures, where a particular protecting group(“PG”), leaving group (“LG”), or transformation condition is depicted,one of ordinary skill in the art will appreciate that other protectinggroups, leaving groups, and transformation conditions are also suitableand are contemplated. Such groups and transformations are described indetail in March's Advanced Organic Chemistry: Reactions, Mechanisms, andStructure, M. B. Smith and J. March, 5^(th) Edition, John Wiley & Sons,2001, Comprehensive Organic Transformations, R. C. Larock, 2n^(d)Edition, John Wiley & Sons, 1999, and Protecting Groups in OrganicSynthesis, T. W. Greene and P. G. M. Wuts, 3r^(d) edition, John Wiley &Sons, 1999, the entirety of each of which is hereby incorporated hereinby reference.

As used herein, the phrase “leaving group” (LG) includes, but is notlimited to, halogens (e.g. fluoride, chloride, bromide, iodide),sulfonates (e.g. mesylate, tosylate, benzenesulfonate, brosylate,nosylate, triflate), diazonium, and the like.

As used herein, the phrase “oxygen protecting group” includes, forexample, carbonyl protecting groups, hydroxyl protecting groups, etc.Hydroxyl protecting groups are well known in the art and include thosedescribed in detail in Protecting Groups in Organic Synthesis, T. W.Greene and P. G. M. Wuts, 3r^(d) edition, John Wiley & Sons, 1999, theentirety of which is incorporated herein by reference. Examples ofsuitable hydroxyl protecting groups include, but are not limited to,esters, allyl ethers, ethers, silyl ethers, alkyl ethers, arylalkylethers, and alkoxyalkyl ethers. Examples of such esters includeformates, acetates, carbonates, and sulfonates. Specific examplesinclude formate, benzoyl formate, chloroacetate, trifluoroacetate,methoxyacetate, triphenylmethoxyacetate, p-chlorophenoxyacetate,3-phenylpropionate, 4-oxopentanoate, 4,4-(ethylenedithio)pentanoate,pivaloate (trimethylacetyl), crotonate, 4-methoxy-crotonate, benzoate,p-benzylbenzoate, 2,4,6-trimethylbenzoate, carbonates such as methyl,9-fluorenylmethyl, ethyl, 2,2,2-trichloroethyl, 2-(trimethylsilyl)ethyl,2-(phenyl sulfonyl)ethyl, vinyl, allyl, and p-nitrobenzyl. Examples ofsuch silyl ethers include trimethylsilyl, triethylsilyl,t-butyldimethylsilyl, t-butyldiphenylsilyl, triisopropylsilyl, and othertrialkylsilyl ethers. Alkyl ethers include methyl, benzyl,p-methoxybenzyl, 3,4-dimethoxybenzyl, trityl, t-butyl, allyl, andallyloxycarbonyl ethers or derivatives. Alkoxyalkyl ethers includeacetals such as methoxymethyl, methylthiomethyl,(2-methoxyethoxy)methyl, benzyloxymethyl,beta-(trimethylsilyl)ethoxymethyl, and tetrahydropyranyl ethers.Examples of arylalkyl ethers include benzyl, p-methoxyb enzyl (MPM),3,4-dimethoxybenzyl, O-nitrobenzyl, p-nitrobenzyl, p-halobenzyl,2,6-dichlorobenzyl, p-cyanobenzyl, and 2- and 4-picolyl.

Amino protecting groups are well known in the art and include thosedescribed in detail in Protecting Groups in Organic Synthesis, T. W.Greene and P. G. M. Wuts, 3^(rd) edition, John Wiley & Sons, 1999, theentirety of which is incorporated herein by reference. Suitable aminoprotecting groups include, but are not limited to, aralkylamines,carbamates, cyclic imides, allyl amines, amides, and the like. Examplesof such groups include t-butyloxycarbonyl (BOC), ethyloxycarbonyl,methyl oxycarbonyl, trichloroethyloxycarbonyl, allyloxycarbonyl (Alloc),benzyloxocarbonyl (CBZ), allyl, phthalimide, benzyl (Bn),fluorenylmethylcarbonyl (Fmoc), formyl, acetyl, chloroacetyl,dichloroacetyl, trichloroacetyl, phenylacetyl, trifluoroacetyl, benzoyl,and the like.

One of skill in the art will appreciate that various functional groupspresent in compounds of the invention such as aliphatic groups,alcohols, carboxylic acids, esters, amides, aldehydes, halogens andnitriles can be interconverted by techniques well known in the artincluding, but not limited to reduction, oxidation, esterification,hydrolysis, partial oxidation, partial reduction, halogenation,dehydration, partial hydration, and hydration. “March's Advanced OrganicChemistry,” 5^(th) Ed., Ed.: Smith, M. B. and March, J., John Wiley &Sons, New York: 2001, the entirety of which is incorporated herein byreference. Such interconversions may require one or more of theaforementioned techniques, and certain methods for synthesizingcompounds of the invention are described below in the Exemplificationand Figures.

4. Uses, Formulation and Administration

Pharmaceutically Acceptable Compositions

According to another embodiment, the invention provides a compositioncomprising a compound of this invention or a pharmaceutically acceptablederivative thereof and a pharmaceutically acceptable carrier, adjuvant,or vehicle. The amount of compound in compositions of this invention issuch that is effective to measurably inhibit or modulate a target RNA,or a mutant thereof, in a biological sample or in a patient. In certainembodiments, the amount of compound in compositions of this invention issuch that is effective to measurably inhibit or modulate a target RNA,in a biological sample or in a patient. In certain embodiments, acomposition of this invention is formulated for administration to apatient in need of such composition. In some embodiments, a compositionof this invention is formulated for oral administration to a patient.

The term “patient,” as used herein, means an animal, preferably amammal, and most preferably a human.

The term “pharmaceutically acceptable carrier, adjuvant, or vehicle”refers to a non-toxic carrier, adjuvant, or vehicle that does notdestroy the pharmacological activity of the compound with which it isformulated. Pharmaceutically acceptable carriers, adjuvants or vehiclesthat may be used in the compositions of this invention include, but arenot limited to, ion exchangers, alumina, aluminum stearate, lecithin,serum proteins, such as human serum albumin, buffer substances such asphosphates, glycine, sorbic acid, potassium sorbate, partial glyceridemixtures of saturated vegetable fatty acids, water, salts orelectrolytes, such as protamine sulfate, disodium hydrogen phosphate,potassium hydrogen phosphate, sodium chloride, zinc salts, colloidalsilica, magnesium trisilicate, polyvinyl pyrrolidone, cellulose-basedsubstances, polyethylene glycol, sodium carboxymethylcellulose,polyacrylates, waxes, polyethylene-polyoxypropylene-block polymers,polyethylene glycol and wool fat.

A “pharmaceutically acceptable derivative” means any non-toxic salt,ester, salt of an ester or other derivative of a compound of thisinvention that, upon administration to a recipient, is capable ofproviding, either directly or indirectly, a compound of this inventionor an inhibitorily active metabolite or residue thereof.

Compositions of the present invention may be administered orally,parenterally, by inhalation spray, topically, rectally, nasally,buccally, vaginally or via an implanted reservoir. The term “parenteral”as used herein includes subcutaneous, intravenous, intramuscular,intra-articular, intra-synovial, intrasternal, intrathecal,intrahepatic, intralesional and intracranial injection or infusiontechniques. Preferably, the compositions are administered orally,intraperitoneally or intravenously. Sterile injectable forms of thecompositions of this invention may be aqueous or oleaginous suspension.These suspensions may be formulated according to techniques known in theart using suitable dispersing or wetting agents and suspending agents.The sterile injectable preparation may also be a sterile injectablesolution or suspension in a non-toxic parenterally acceptable diluent orsolvent, for example as a solution in 1,3-butanediol. Among theacceptable vehicles and solvents that may be employed are water,Ringer's solution and isotonic sodium chloride solution. In addition,sterile, fixed oils are conventionally employed as a solvent orsuspending medium.

For this purpose, any bland fixed oil may be employed includingsynthetic mono- or di-glycerides. Fatty acids, such as oleic acid andits glyceride derivatives are useful in the preparation of injectables,as are natural pharmaceutically-acceptable oils, such as olive oil orcastor oil, especially in their polyoxyethylated versions. These oilsolutions or suspensions may also contain a long-chain alcohol diluentor dispersant, such as carboxymethyl cellulose or similar dispersingagents that are commonly used in the formulation of pharmaceuticallyacceptable dosage forms including emulsions and suspensions. Othercommonly used surfactants, such as Tweens, Spans and other emulsifyingagents or bioavailability enhancers which are commonly used in themanufacture of pharmaceutically acceptable solid, liquid, or otherdosage forms may also be used for the purposes of formulation.

Pharmaceutically acceptable compositions of this invention may be orallyadministered in any orally acceptable dosage form including, but notlimited to, capsules, tablets, aqueous suspensions or solutions. In thecase of tablets for oral use, carriers commonly used include lactose andcorn starch. Lubricating agents, such as magnesium stearate, are alsotypically added. For oral administration in a capsule form, usefuldiluents include lactose and dried cornstarch. When aqueous suspensionsare required for oral use, the active ingredient is combined withemulsifying and suspending agents. If desired, certain sweetening,flavoring or coloring agents may also be added.

Alternatively, pharmaceutically acceptable compositions of thisinvention may be administered in the form of suppositories for rectaladministration. These can be prepared by mixing the agent with asuitable non-irritating excipient that is solid at room temperature butliquid at rectal temperature and therefore will melt in the rectum torelease the drug. Such materials include cocoa butter, beeswax andpolyethylene glycols.

Pharmaceutically acceptable compositions of this invention may also beadministered topically, especially when the target of treatment includesareas or organs readily accessible by topical application, includingdiseases of the eye, the skin, or the lower intestinal tract. Suitabletopical formulations are readily prepared for each of these areas ororgans.

Topical application for the lower intestinal tract can be effected in arectal suppository formulation (see above) or in a suitable enemaformulation. Topically-transdermal patches may also be used.

For topical applications, provided pharmaceutically acceptablecompositions may be formulated in a suitable ointment containing theactive component suspended or dissolved in one or more carriers.Carriers for topical administration of compounds of this inventioninclude, but are not limited to, mineral oil, liquid petrolatum, whitepetrolatum, propylene glycol, polyoxyethylene, polyoxypropylenecompound, emulsifying wax and water. Alternatively, providedpharmaceutically acceptable compositions can be formulated in a suitablelotion or cream containing the active components suspended or dissolvedin one or more pharmaceutically acceptable carriers. Suitable carriersinclude, but are not limited to, mineral oil, sorbitan monostearate,polysorbate 60, cetyl esters wax, cetearyl alcohol, 2-octyldodecanol,benzyl alcohol and water.

For ophthalmic use, provided pharmaceutically acceptable compositionsmay be formulated as micronized suspensions in isotonic, pH adjustedsterile saline, or, preferably, as solutions in isotonic, pH adjustedsterile saline, either with or without a preservative such asbenzylalkonium chloride. Alternatively, for ophthalmic uses, thepharmaceutically acceptable compositions may be formulated in anointment such as petrolatum.

Pharmaceutically acceptable compositions of this invention may also beadministered by nasal aerosol or inhalation. Such compositions areprepared according to techniques well-known in the art of pharmaceuticalformulation and may be prepared as solutions in saline, employing benzylalcohol or other suitable preservatives, absorption promoters to enhancebioavailability, fluorocarbons, and/or other conventional solubilizingor dispersing agents.

Most preferably, pharmaceutically acceptable compositions of thisinvention are formulated for oral administration. Such formulations maybe administered with or without food. In some embodiments,pharmaceutically acceptable compositions of this invention areadministered without food. In other embodiments, pharmaceuticallyacceptable compositions of this invention are administered with food.

The amount of compounds of the present invention that may be combinedwith the carrier materials to produce a composition in a single dosageform will vary depending upon the host treated, the particular mode ofadministration. Preferably, provided compositions should be formulatedso that a dosage of between 0.01-100 mg/kg body weight/day of theinhibitor can be administered to a patient receiving these compositions.

It should also be understood that a specific dosage and treatmentregimen for any particular patient will depend upon a variety offactors, including the activity of the specific compound employed, theage, body weight, general health, sex, diet, time of administration,rate of excretion, drug combination, and the judgment of the treatingphysician and the severity of the particular disease being treated. Theamount of a compound of the present invention in the composition willalso depend upon the particular compound in the composition.

Uses of Compounds and Pharmaceutically Acceptable Compositions

Compounds and compositions described herein are generally useful for themodulation of a target RNA to retreat an RNA-mediated disease orcondition.

The activity of a compound utilized in this invention to modulate atarget RNA may be assayed in vitro, in vivo or in a cell line. In vitroassays include assays that determine modulation of the target RNA.Alternate in vitro assays quantitate the ability of the compound to bindto the target RNA. Detailed conditions for assaying a compound utilizedin this invention to modulate a target RNA are set forth in the Examplesbelow.

As used herein, the terms “treatment,” “treat,” and “treating” refer toreversing, alleviating, delaying the onset of, or inhibiting theprogress of a disease or disorder, or one or more symptoms thereof, asdescribed herein. In some embodiments, treatment may be administeredafter one or more symptoms have developed. In other embodiments,treatment may be administered in the absence of symptoms. For example,treatment may be administered to a susceptible individual prior to theonset of symptoms (e.g., in light of a history of symptoms and/or inlight of genetic or other susceptibility factors). Treatment may also becontinued after symptoms have resolved, for example to prevent or delaytheir recurrence.

Provided compounds are modulators of a target RNA and are thereforeuseful for treating one or more disorders associated with or affected by(e.g., downstream of) the target RNA. Thus, in certain embodiments, thepresent invention provides a method for treating an RNA-mediateddisorder comprising the step of administering to a patient in needthereof a compound of the present invention, or pharmaceuticallyacceptable composition thereof.

As used herein, the terms “RNA-mediated” disorders, diseases, and/orconditions as used herein means any disease or other deleteriouscondition in which RNA, such as an overexpressed, underexpressed,mutant, misfolded, pathogenic, or ongogenic RNA, is known to play arole. Accordingly, another embodiment of the present invention relatesto treating or lessening the severity of one or more diseases in whichRNA, such as an overexpressed, underexpressed, mutant, misfolded,pathogenic, or ongogenic RNA, is known to play a role.

In some embodiments, the present invention provides a method fortreating one or more disorders, diseases, and/or conditions wherein thedisorder, disease, or condition includes, but is not limited to, acellular proliferative disorder.

Cellular Proliferative Disorders

The present invention features methods and compositions for thediagnosis and prognosis of cellular proliferative disorders (e.g.,cancer) and the treatment of these disorders by modulating a target RNA.Cellular proliferative disorders described herein include, e.g., cancer,obesity, and proliferation-dependent diseases. Such disorders may bediagnosed using methods known in the art.

Cancer

Cancer includes, in one embodiment, without limitation, leukemias (e.g.,acute leukemia, acute lymphocytic leukemia, acute myelocytic leukemia,acute myeloblastic leukemia, acute promyelocytic leukemia, acutemyelomonocytic leukemia, acute monocytic leukemia, acuteerythroleukemia, chronic leukemia, chronic myelocytic leukemia, chroniclymphocytic leukemia), polycythemia vera, lymphoma (e.g., Hodgkin'sdisease or non-Hodgkin's disease), Waldenstrom's macroglobulinemia,multiple myeloma, heavy chain disease, and solid tumors such as sarcomasand carcinomas (e.g., fibrosarcoma, myxosarcoma, liposarcoma,chondrosarcoma, osteogenic sarcoma, chordoma, angiosarcoma,endotheliosarcoma, lymphangiosarcoma, lymphangioendotheliosarcoma,synovioma, mesothelioma, Ewing's tumor, leiomyosarcoma,rhabdomyosarcoma, colon carcinoma, pancreatic cancer, breast cancer,ovarian cancer, prostate cancer, squamous cell carcinoma, basal cellcarcinoma, adenocarcinoma, sweat gland carcinoma, sebaceous glandcarcinoma, papillary carcinoma, papillary adenocarcinomas,cystadenocarcinoma, medullary carcinoma, bronchogenic carcinoma, renalcell carcinoma, hepatoma, bile duct carcinoma, choriocarcinoma,seminoma, embryonal carcinoma, Wilm's tumor, cervical cancer, uterinecancer, testicular cancer, lung carcinoma, small cell lung carcinoma,bladder carcinoma, epithelial carcinoma, glioma, astrocytoma,medulloblastoma, craniopharyngioma, ependymoma, pinealoma,hemangioblastoma, acoustic neuroma, oligodendroglioma, schwannoma,meningioma, melanoma, neuroblastoma, and retinoblastoma). In someembodiments, the cancer is melanoma or breast cancer.

Cancers includes, in another embodiment, without limitation,mesothelioma, hepatobilliary (hepatic and billiary duct), bone cancer,pancreatic cancer, skin cancer, cancer of the head or neck, cutaneous orintraocular melanoma, ovarian cancer, colon cancer, rectal cancer,cancer of the anal region, stomach cancer, gastrointestinal (gastric,colorectal, and duodenal), uterine cancer, carcinoma of the fallopiantubes, carcinoma of the endometrium, carcinoma of the cervix, carcinomaof the vagina, carcinoma of the vulva, Hodgkin's Disease, cancer of theesophagus, cancer of the small intestine, cancer of the endocrinesystem, cancer of the thyroid gland, cancer of the parathyroid gland,cancer of the adrenal gland, sarcoma of soft tissue, cancer of theurethra, cancer of the penis, prostate cancer, testicular cancer,chronic or acute leukemia, chronic myeloid leukemia, lymphocyticlymphomas, cancer of the bladder, cancer of the kidney or ureter, renalcell carcinoma, carcinoma of the renal pelvis, non-Hodgkins' s lymphoma,spinal axis tumors, brain stem glioma, pituitary adenoma, adrenocorticalcancer, gall bladder cancer, multiple myeloma, cholangiocarcinoma,fibrosarcoma, neuroblastoma, retinoblastoma, or a combination of one ormore of the foregoing cancers.

In some embodiments, the present invention provides a method fortreating a tumor in a patient in need thereof, comprising administeringto the patient any of the compounds, salts or pharmaceuticalcompositions described herein. In some embodiments, the tumor comprisesany of the cancers described herein. In some embodiments, the tumorcomprises melanoma cancer. In some embodiments, the tumor comprisesbreast cancer. In some embodiments, the tumor comprises lung cancer. Insome embodiments the the tumor comprises small cell lung cancer (SCLC).In some embodiments the the tumor comprises non-small cell lung cancer(NSCLC).

In some embodiments, the tumor is treated by arresting further growth ofthe tumor. In some embodiments, the tumor is treated by reducing thesize (e.g., volume or mass) of the tumor by at least 5%, 10%, 25%, 50%,75%, 90% or 99% relative to the size of the tumor prior to treatment. Insome embodiments, tumors are treated by reducing the quantity of thetumors in the patient by at least 5%, 10%, 25%, 50%, 75%, 90% or 99%relative to the quantity of tumors prior to treatment.

Other Proliferative Diseases

Other proliferative diseases include, e.g., obesity, benign prostatichyperplasia, psoriasis, abnormal keratinization, lymphoproliferativedisorders (e.g., a disorder in which there is abnormal proliferation ofcells of the lymphatic system), chronic rheumatoid arthritis,arteriosclerosis, restenosis, and diabetic retinopathy. Proliferativediseases that are hereby incorporated by reference include thosedescribed in U.S. Pat. Nos. 5,639,600 and 7,087,648.

Inflammatory Disorders and Diseases

Compounds of the invention are also useful in the treatment ofinflammatory or allergic conditions of the skin, for example psoriasis,contact dermatitis, atopic dermatitis, alopecia areata, erythemamultiforma, dermatitis herpetiformis, scleroderma, vitiligo,hypersensitivity angiitis, urticaria, bullous pemphigoid, lupuserythematosus, systemic lupus erythematosus, pemphigus vulgaris,pemphigus foliaceus, paraneoplastic pemphigus, epidermolysis bullosaacquisita, acne vulgaris, and other inflammatory or allergic conditionsof the skin.

Compounds of the invention may also be used for the treatment of otherdiseases or conditions, such as diseases or conditions having aninflammatory component, for example, treatment of diseases andconditions of the eye such as ocular allergy, conjunctivitis,keratoconjunctivitis sicca, and vernal conjunctivitis, diseasesaffecting the nose including allergic rhinitis, and inflammatory diseasein which autoimmune reactions are implicated or having an autoimmunecomponent or etiology, including autoimmune hematological disorders(e.g. hemolytic anemia, aplastic anemia, pure red cell anemia andidiopathic thrombocytopenia), systemic lupus erythematosus, rheumatoidarthritis, polychondritis, scleroderma, Wegener granulamatosis,dermatomyositis, chronic active hepatitis, myasthenia gravis,Steven-Johnson syndrome, idiopathic sprue, autoimmune inflammatory boweldisease (e.g. ulcerative colitis and Crohn's disease), irritable bowelsyndrome, celiac disease, periodontitis, hyaline membrane disease,kidney disease, glomerular disease, alcoholic liver disease, multiplesclerosis, endocrine opthalmopathy, Grave's disease, sarcoidosis,alveolitis, chronic hypersensitivity pneumonitis, multiple sclerosis,primary biliary cirrhosis, uveitis (anterior and posterior), Sjogren'ssyndrome, keratoconjunctivitis sicca and vernal keratoconjunctivitis,interstitial lung fibrosis, psoriatic arthritis, systemic juvenileidiopathic arthritis, cryopyrin-associated periodic syndrome, nephritis,vasculitis, diverticulitis, interstitial cystitis, glomerulonephritis(with and without nephrotic syndrome, e.g. including idiopathicnephrotic syndrome or minal change nephropathy), chronic granulomatousdisease, endometriosis, leptospiriosis renal disease, glaucoma, retinaldisease, ageing, headache, pain, complex regional pain syndrome, cardiachypertrophy, musclewasting, catabolic disorders, obesity, fetal growthretardation, hyperchlolesterolemia, heart disease, chronic heartfailure, mesothelioma, anhidrotic ecodermal dysplasia, Behcet's disease,incontinentia pigmenti, Paget's disease, pancreatitis, hereditaryperiodic fever syndrome, asthma (allergic and non-allergic, mild,moderate, severe, bronchitic, and exercise-induced), acute lung injury,acute respiratory distress syndrome, eosinophilia, hypersensitivities,anaphylaxis, nasal sinusitis, ocular allergy, silica induced diseases,COPD (reduction of damage, airways inflammation, bronchialhyperreactivity, remodeling or disease progression), pulmonary disease,cystic fibrosis, acid-induced lung injury, pulmonary hypertension,polyneuropathy, cataracts, muscle inflammation in conjunction withsystemic sclerosis, inclusion body myositis, myasthenia gravis,thyroiditis, Addison's disease, lichen planus, Type 1 diabetes, or Type2 diabetes, appendicitis, atopic dermatitis, asthma, allergy,blepharitis, bronchiolitis, bronchitis, bursitis, cervicitis,cholangitis, cholecystitis, chronic graft rejection, colitis,conjunctivitis, Crohn's disease, cystitis, dacryoadenitis, dermatitis,dermatomyositis, encephalitis, endocarditis, endometritis, enteritis,enterocolitis, epicondylitis, epididymitis, fasciitis, fibrositis,gastritis, gastroenteritis, Henoch-Schonlein purpura, hepatitis,hidradenitis suppurativa, immunoglobulin A nephropathy, interstitiallung disease, laryngitis, mastitis, meningitis, myelitis myocarditis,myositis, nephritis, oophoritis, orchitis, osteitis, otitis,pancreatitis, parotitis, pericarditis, peritonitis, pharyngitis,pleuritis, phlebitis, pneumonitis, pneumonia, polymyositis, proctitis,prostatitis, pyelonephritis, rhinitis, salpingitis, sinusitis,stomatitis, synovitis, tendonitis, tonsillitis, ulcerative colitis,uveitis, vaginitis, vasculitis, or vulvitis.

In some embodiments the inflammatory disease which can be treatedaccording to the methods of this invention is an disease of the skin. Insome embodiments, the inflammatory disease of the skin is selected fromcontact dermatitits, atompic dermatitis, alopecia areata, erythemamultiforma, dermatitis herpetiformis, scleroderma, vitiligo,hypersensitivity angiitis, urticaria, bullous pemphigoid, pemphigusvulgaris, pemphigus foliaceus, paraneoplastic pemphigus, epidermolysisbullosa acquisita, and other inflammatory or allergic conditions of theskin.

In some embodiments the inflammatory disease which can be treatedaccording to the methods of this invention is selected from acute andchronic gout, chronic gouty arthritis, psoriasis, psoriatic arthritis,rheumatoid arthritis, Juvenile rheumatoid arthritis, Systemic jubenileidiopathic arthritis (SJIA), Cryopyrin Associated Periodic Syndrome(CAPS), and osteoarthritis.

In some embodiments the inflammatory disease which can be treatedaccording to the methods of this invention is a TH17 mediated disease.In some embodiments the TH17 mediated disease is selected from Systemiclupus erythematosus, Multiple sclerosis, and inflammatory bowel disease(including Crohn's disease or ulcerative colitis).

In some embodiments the inflammatory disease which can be treatedaccording to the methods of this invention is selected from Sjogren'ssyndrome, allergic disorders, osteoarthritis, conditions of the eye suchas ocular allergy, conjunctivitis, keratoconjunctivitis sicca and vernalconjunctivitis, and diseases affecting the nose such as allergicrhinitis.

Metabolic Disease

In some embodiments the invention provides a method of treating ametabolic disease. In some embodiments the metabolic disease is selectedfrom Type 1 diabetes, Type 2 diabetes, metabolic syndrome or obesity.

The compounds and compositions, according to the method of the presentinvention, may be administered using any amount and any route ofadministration effective for treating or lessening the severity of acancer, an autoimmune disorder, a proliferative disorder, aninflammatory disorder, a neurodegenerative or neurological disorder,schizophrenia, a bone-related disorder, liver disease, or a cardiacdisorder. The exact amount required will vary from subject to subject,depending on the species, age, and general condition of the subject, theseverity of the infection, the particular agent, its mode ofadministration, and the like. Compounds of the invention are preferablyformulated in dosage unit form for ease of administration and uniformityof dosage. The expression “dosage unit form” as used herein refers to aphysically discrete unit of agent appropriate for the patient to betreated. It will be understood, however, that the total daily usage ofthe compounds and compositions of the present invention will be decidedby the attending physician within the scope of sound medical judgment.The specific effective dose level for any particular patient or organismwill depend upon a variety of factors including the disorder beingtreated and the severity of the disorder; the activity of the specificcompound employed; the specific composition employed; the age, bodyweight, general health, sex and diet of the patient; the time ofadministration, route of administration, and rate of excretion of thespecific compound employed; the duration of the treatment; drugs used incombination or coincidental with the specific compound employed, andlike factors well known in the medical arts. The term “patient,” as usedherein, means an animal, preferably a mammal, and most preferably ahuman.

Pharmaceutically acceptable compositions of this invention can beadministered to humans and other animals orally, rectally, parenterally,intracisternally, intravaginally, intraperitoneally, topically (as bypowders, ointments, or drops), bucally, as an oral or nasal spray, orthe like, depending on the severity of the infection being treated. Incertain embodiments, the compounds of the invention may be administeredorally or parenterally at dosage levels of about 0.01 mg/kg to about 50mg/kg and preferably from about 1 mg/kg to about 25 mg/kg, of subjectbody weight per day, one or more times a day, to obtain the desiredtherapeutic effect.

Liquid dosage forms for oral administration include, but are not limitedto, pharmaceutically acceptable emulsions, microemulsions, solutions,suspensions, syrups and elixirs. In addition to the active compounds,the liquid dosage forms may contain inert diluents commonly used in theart such as, for example, water or other solvents, solubilizing agentsand emulsifiers such as ethyl alcohol, isopropyl alcohol, ethylcarbonate, ethyl acetate, benzyl alcohol, benzyl benzoate, propyleneglycol, 1,3-butylene glycol, dimethylformamide, oils (in particular,cottonseed, groundnut, corn, germ, olive, castor, and sesame oils),glycerol, tetrahydrofurfuryl alcohol, polyethylene glycols and fattyacid esters of sorbitan, and mixtures thereof. Besides inert diluents,the oral compositions can also include adjuvants such as wetting agents,emulsifying and suspending agents, sweetening, flavoring, and perfumingagents.

Injectable preparations, for example, sterile injectable aqueous oroleaginous suspensions may be formulated according to the known artusing suitable dispersing or wetting agents and suspending agents. Thesterile injectable preparation may also be a sterile injectablesolution, suspension or emulsion in a nontoxic parenterally acceptablediluent or solvent, for example, as a solution in 1,3-butanediol. Amongthe acceptable vehicles and solvents that may be employed are water,Ringer's solution, U. S.P. and isotonic sodium chloride solution. Inaddition, sterile, fixed oils are conventionally employed as a solventor suspending medium. For this purpose any bland fixed oil can beemployed including synthetic mono- or diglycerides. In addition, fattyacids such as oleic acid are used in the preparation of injectables.

Injectable formulations can be sterilized, for example, by filtrationthrough a bacterial-retaining filter, or by incorporating sterilizingagents in the form of sterile solid compositions which can be dissolvedor dispersed in sterile water or other sterile injectable medium priorto use.

In order to prolong the effect of a compound of the present invention,it is often desirable to slow the absorption of the compound fromsubcutaneous or intramuscular injection. This may be accomplished by theuse of a liquid suspension of crystalline or amorphous material withpoor water solubility. The rate of absorption of the compound thendepends upon its rate of dissolution that, in turn, may depend uponcrystal size and crystalline form. Alternatively, delayed absorption ofa parenterally administered compound form is accomplished by dissolvingor suspending the compound in an oil vehicle. Injectable depot forms aremade by forming microencapsule matrices of the compound in biodegradablepolymers such as polylactide-polyglycolide. Depending upon the ratio ofcompound to polymer and the nature of the particular polymer employed,the rate of compound release can be controlled. Examples of otherbiodegradable polymers include poly(orthoesters) and poly(anhydrides).Depot injectable formulations are also prepared by entrapping thecompound in liposomes or microemulsions that are compatible with bodytissues.

Compositions for rectal or vaginal administration are preferablysuppositories which can be prepared by mixing the compounds of thisinvention with suitable non-irritating excipients or carriers such ascocoa butter, polyethylene glycol or a suppository wax which are solidat ambient temperature but liquid at body temperature and therefore meltin the rectum or vaginal cavity and release the active compound.

Solid dosage forms for oral administration include capsules, tablets,pills, powders, and granules. In such solid dosage forms, the activecompound is mixed with at least one inert, pharmaceutically acceptableexcipient or carrier such as sodium citrate or dicalcium phosphateand/or a) fillers or extenders such as starches, lactose, sucrose,glucose, mannitol, and silicic acid, b) binders such as, for example,carboxymethylcellulose, alginates, gelatin, polyvinylpyrrolidinone,sucrose, and acacia, c) humectants such as glycerol, d) disintegratingagents such as agar-agar, calcium carbonate, potato or tapioca starch,alginic acid, certain silicates, and sodium carbonate, e) solutionretarding agents such as paraffin, f) absorption accelerators such asquaternary ammonium compounds, g) wetting agents such as, for example,cetyl alcohol and glycerol monostearate, h) absorbents such as kaolinand bentonite clay, and i) lubricants such as talc, calcium stearate,magnesium stearate, solid polyethylene glycols, sodium lauryl sulfate,and mixtures thereof In the case of capsules, tablets and pills, thedosage form may also comprise buffering agents.

Solid compositions of a similar type may also be employed as fillers insoft and hard-filled gelatin capsules using such excipients as lactoseor milk sugar as well as high molecular weight polyethylene glycols andthe like. The solid dosage forms of tablets, dragees, capsules, pills,and granules can be prepared with coatings and shells such as entericcoatings and other coatings well known in the pharmaceutical formulatingart. They may optionally contain opacifying agents and can also be of acomposition that they release the active ingredient(s) only, orpreferentially, in a certain part of the intestinal tract, optionally,in a delayed manner. Examples of embedding compositions that can be usedinclude polymeric substances and waxes. Solid compositions of a similartype may also be employed as fillers in soft and hard-filled gelatincapsules using such excipients as lactose or milk sugar as well as highmolecular weight polethylene glycols and the like.

The active compounds can also be in micro-encapsulated form with one ormore excipients as noted above. The solid dosage forms of tablets,dragees, capsules, pills, and granules can be prepared with coatings andshells such as enteric coatings, release controlling coatings and othercoatings well known in the pharmaceutical formulating art. In such soliddosage forms the active compound may be admixed with at least one inertdiluent such as sucrose, lactose or starch. Such dosage forms may alsocomprise, as is normal practice, additional substances other than inertdiluents, e.g., tableting lubricants and other tableting aids such amagnesium stearate and microcrystalline cellulose. In the case ofcapsules, tablets and pills, the dosage forms may also comprisebuffering agents. They may optionally contain opacifying agents and canalso be of a composition that they release the active ingredient(s)only, or preferentially, in a certain part of the intestinal tract,optionally, in a delayed manner. Examples of embedding compositions thatcan be used include polymeric substances and waxes.

Dosage forms for topical or transdermal administration of a compound ofthis invention include ointments, pastes, creams, lotions, gels,powders, solutions, sprays, inhalants or patches. The active componentis admixed under sterile conditions with a pharmaceutically acceptablecarrier and any needed preservatives or buffers as may be required.Ophthalmic formulation, ear drops, and eye drops are also contemplatedas being within the scope of this invention. Additionally, the presentinvention contemplates the use of transdermal patches, which have theadded advantage of providing controlled delivery of a compound to thebody. Such dosage forms can be made by dissolving or dispensing thecompound in the proper medium. Absorption enhancers can also be used toincrease the flux of the compound across the skin. The rate can becontrolled by either providing a rate controlling membrane or bydispersing the compound in a polymer matrix or gel.

According to one embodiment, the invention relates to a method ofmodulating the activity of a target RNA in a biological samplecomprising the step of contacting said biological sample with a compoundof this invention, or a composition comprising said compound.

According to another embodiment, the invention relates to a method ofmodulating the activity of a target RNA in a biological samplecomprising the step of contacting said biological sample with a compoundof this invention, or a composition comprising said compound. In certainembodiments, the invention relates to a method of irreversiblyinhibiting the activity of a target RNA in a biological samplecomprising the step of contacting said biological sample with a compoundof this invention, or a composition comprising said compound.

The term “biological sample”, as used herein, includes, withoutlimitation, cell cultures or extracts thereof; biopsied materialobtained from a mammal or extracts thereof; and blood, saliva, urine,feces, semen, tears, cerebrospinal fluid, or other body fluids orextracts thereof.

Another embodiment of the present invention relates to a method ofmodulating the activity of a target RNA in a patient comprising the stepof administering to said patient a compound of the present invention, ora composition comprising said compound.

According to another embodiment, the invention relates to a method ofinhibiting the activity of a target RNA in a patient comprising the stepof administering to said patient a compound of the present invention, ora composition comprising said compound. According to certainembodiments, the invention relates to a method of irreversiblyinhibiting the activity of a target RNA in a patient comprising the stepof administering to said patient a compound of the present invention, ora composition comprising said compound. In other embodiments, thepresent invention provides a method for treating a disorder mediated bya target RNA in a patient in need thereof, comprising the step ofadministering to said patient a compound according to the presentinvention or pharmaceutically acceptable composition thereof. Suchdisorders are described in detail herein.

EXEMPLIFICATION

As depicted in the Examples below, exemplary compounds are preparedaccording to the following general procedures and used in biologicalassays and other procedures described generally herein. It will beappreciated that, although the general methods depict the synthesis ofcertain compounds of the present invention, the following generalmethods, and other methods known to one of ordinary skill in the art,can be applied to all compounds and subclasses and species of each ofthese compounds, as described herein. Similarly, assays and otheranalyses can be adapted according to the knowledge of one of ordinaryskill in the art.

Example 1 Application of Photoprobes to Locate and Quantify Sites ofModifications in RNA

As discussed above, a variety of RNA molecules play important regulatoryroles in cells. RNA secondary and tertiary structures are critical forthese regulatory activities. Various tools are available for determiningRNA structure. One of the most effective methods is SHAPE (selective2′-hydroxyl acylation and primer extension). This methodology takesadvantage of the characteristic that the ribose group in all RNAs has a2′-hydroxyl whose reactivity is affected by local nucleotide flexibilityand accessability to solvent. This 2′-hydroxyl is reactive in regions ofthe RNA that are single-stranded and flexible, but is unreactive atnucleotides that are base-paired. In other words, SHAPE reactivity isinversely proportional to the probability that a nucleotide is basepaired within an RNA secondary structure. Reagents that chemicallymodify the RNA at this 2′-hydroxyl can be used as probes to discern RNAstructure. SHAPE reagents include small-molecules such as1-methyl-7-nitroisatoic anhydride (1M7) and benzoyl cyanide (BzCN) thatreact with the 2′-hydroxyl group of flexible nucleotides to form a2′-O-adduct. Other acylation electrophiles such as2-methylnicotinic acidimidazolide (NAI) and2-methyl-3-furoic acid imidazolide (FAI) can beutilized.

One useful aspect of the present invention is the tethering of aRNA-binding small molecule ligand to a photoprobe. This links thephotoactivation-mediated covalent modification event with the ligandbinding event such that the photoprobe is most likely to react with aportion of the RNA that is proximal (e.g., near in space) to the bindingsite of the ligand. Thus, the modification pattern on the RNA will bedecisively altered because the activity of the photoactivatable agentwill be constrained to nucleotides proximal to ligand binding pockets onthe RNA. Thus, one can infer the existence and the location of ligandbinding pockets from the altered reactivity pattern, as revealed inappropriate analytical methods such as sequencing.

The SHAPE-MaP approach exploits conditions that cause reversetranscriptase to misread SHAPE-modified nucleotides and incorporate anucleotide non-complementary to the original sequence into the newlysynthesized cDNA. The positions and relative frequencies of SHAPEadducts are recorded as mutations in the cDNA primary sequence. In aSHAPE-MaP experiment, the RNA is treated with a SHAPE reagent or treatedwith solvent only, and the RNA is modified. RNA from each experimentalcondition is reverse-transcribed, and the resulting cDNAs are thensequenced. Reactive positions are identified by subtracting data for thetreated sample from data obtained for the untreated sample and bynormalizing to data for a denatured (unfolded) control RNA.

SHAPE-MaP can be performed and analyzed according to detailed publishedmethods (Martin et al., RNA 2012; 18:77-87; McGuinness et al., J. Am.Chem. Soc. 2012; 134:6617-6624; Siegfried et al., Nature Methods 2014;11:959-965; Lavender et al., PLoS Comput. Biol. 2015; 11(5)e1004230;McGuinness et al., Proc. Natl. Acad. Sci. USA 2015; 112:2425-2430). TheSHAPE-MaP sequence data can be analyzed using ShapeFinder (Vasa et al.,RNA 2008; 14:1979-1990) or ShapeMapper (Siegfried et al., Nature Methods2014; 11:959-965) or other software. Each of the foregoing publicationsis hereby incorporated by reference.

PEARL-seq (Proximity-Enhanced Activation via RNA Ligation-sequencing)departs from SHAPE and SHAPE-MaP in that it uses a tether to link theacylation event to a ligand binding event, thus decisively altering theacylation pattern, which is observed as ‘mutations’ in the sequencing,because only riboses proximal to ligand binding pockets will beacylated. From this one infers the existence of small-molecule bindingsites on the targeted RNA as well as the location of those ligandbinding sites across the transcriptome. Those RNA ligand/tether/warheadconstructs (hooks') that also bear a click functional group can bepulled down by clicking to a clickable biotin and then complexing withstreptavidin on beads. This click/pull-down protocol enables sequencingof only those RNAs that have been covalently modified by a ‘hook’.SHAPE-MaP & RING-MaP protocols carried out separately on the targetedRNAs enable the building of structural models of targeted RNAs as aframework that will enhance the interpretation of “covalent affinitytranscriptomics” sequence data. Success is measured by bioactivities offree ligands in cells.

Libraries for use in the present invention will contain small molecules(“RNA ligands”) tethered to electrophilic warheads that selectively formcovalent bonds with nucleotides proximal to the binding site in thetarget RNA. The library's diversity encompasses variation in RNA ligandstructure, tether structure, and warhead structure.

The RNA ligands are designed based on hypotheses about the structuraldeterminant of RNA affinity and then synthesized and attached to thetether and warhead. As an example, Lau and coworkers used SELEX(systematic evolution of ligands by exponential enrichment) to evolve ashort RNA sequence termed Aptamer-21 as a high-affinity RNA aptamer(K_(d)=50 nM) against a heteroaryldihydropyrimidine structure, compound1b (I-1 herein) below:

(Lau, J. L.; Baksh, M. M.; Fiedler, J. D.; Brown, S. D.; Kussrow, A.;Bornhop, D. J.; Ordoukhanian, P.; Finn, M. G. ACS Nano, 2011, 5,7722-7729; for more information on SELEX, see also, e.g., a) S. E.Osborne, A. D. Ellington, Chem. Rev. 1997, 97, 349-370; b) L. Gold, D.Brown, Y. Y. He, T. Shtatland, B. S. Singer, Y. Wu, Proc. Natl. Acad.Sci. USA 1997, 94, 59-64; c) L. Gold, B. Polisky, 0. Uhlenbeck, M. Yams,Annu. Rev. Biochem. 1995, 64, 763-797.) This structure was chosen as arepresentative drug-like molecule with no cross-reactivity withmammalian or bacterial cells. The authors also embedded Aptamer 21, itsweaker-binding variants, and a known aptamer against theophylline in alonger RNA sequence that was encapsidated inside a virus-like particleby an expression technique. These nucleoprotein particles were shown bybackscattering interferometry to bind to the small-molecule ligands withaffinities similar to those of the free (nonencapsidated) aptamers.Compound I-1 is water-soluble, nontoxic, and sufficiently dissimilar instructure to native biological molecules to minimize off-target binding.It features a 1,4-triazole linkage installed with copper-catalyzedazide-alkyne cycloaddition (CuAAC) chemistry, which enables convenientconnection of the ligand to other molecules of interest. Other HAPvariants described herein are expected to have similarly advantageousproperties. Furthermore, use of the Aptamer 21 RNA as a starting pointoffers the advantage of a well-characterized RNA of known structure andwhose binding mode with I-1 can be verified by reference to the originalpublication. Aptamer 21 has the following sequence:

(SEQ. ID: 25) GGGUAGGCCAGGCAGCCAACUAGCGAGAGCUUAAAUCUCUGAGCCCGAGAGGGUUCAGUGCUGCUUAUGUGGACGGCU.

Alternatively, the RNA ligands are selected from commercially availablesources based on their similarity to known RNA ligands orcomplementarity to RNA binding pockets, purchased, and subjected tofurther synthesis to attach to the tether and warhead. Examples includebut are not limited to: tetracycline antibiotics, aminoglycosideantibiotics, theophylline and similar structures (e.g., xanthines),ribocil and similar structures, linezolid and similar structures. In athird and complementary approach, libraries of RNA ligands are preparedusing combinatorial chemistry techniques. Specifically, the tethers ofchoice are affixed to polymers that support organic synthesis, andthrough a series of synthetic chemistry steps, compounds are made in aone-bead-one-compound format. These steps lead to the incorporation inthe final RNA ligand a wide range of fragments and reactants connectedby a wide range of functional groups. Those compounds are released andthe final off-bead step is attachment of the RNA warhead.

As a key element of the library's functional outcome, for each RNAligand and RNA warhead, a number of structurally diverse tethers areincorporated in order to optimize tether length, tether flexibility, andthe ability to tolerate additional functionality (in particular, clickfunctional groups). Specific tethers that are explored includeoligoethylene glycols containing one to six ethylene units,oligopeptides that are highly flexible (e.g., oligoglycines oroligo-N-methylglycines containing one to six amino acids) or more rigid(e.g., oligoprolines or oligo-4-hydroxyprolines containing one to sixamino acids). Incorporation of click functional groups into theoligoethylene glycol tethers requires insertion of an amino acid,bearing a clickable functional group, at either the RNA ligand or theRNA warhead end of the tether. Incorporation of click functional groupsinto the oligopeptides tethers simply requires replacing any one of theamino acid residues with an amino acid bearing the clickable functionalgroup.

The RNA warheads are selected from known or modified photoactivatablefunctional groups. Additional warheads will be identified by (1)synthetic modifications to the aforementioned warheads to establish thestructure/activity relationship for RNA warheads as well as (2)screening commercially available photoactivatable groups.

Click functional groups are selected from the standard ‘toolkit’ ofpublished click reagents and reactants. The present work focuses onazides, alkynes (both terminal and strained), dienes, tetrazines, anddienophiles.

Further details of the SHAPE, SHAPE-MaP, and PEARL-seq methods,including alternate reagents, conditions, and data analysis aredescribed in WO 2017/136450, WO 2015/054247, US 2014/0154673, U.S. Pat.No. 7,745,614, and U.S. Pat. No. 8,313,424, each of which is herebyincorporated by reference in its entirety.

Example 2 Preparation of CPNQ Analogues and Other Quinoline-BasedLigands

Exemplary small molecule ligands based on CPNQ and other quinolinescaffolds may be prepared based on the synthetic schemes shown inWO2017/136450, which is hereby incorporated by reference in itsentirety.

Example 3 Synthesis of Exemplary Photoprobe Compounds

General: Unless otherwise noted, all reactions were conducted under anN₂ atmosphere. All solvents and reagents were used as received withoutfurther purification. Compound 1 was synthesized as previously describedin Lau, J. L.; Baksh, M. M.; Fiedler, J. D.; Brown, S. D.; Kussrow, A.;Bornhop, D. J.; Ordoukhanian, P.; Finn, M. G. ACS Nano, 2011, 5,7722-7729. 3-azido—S—(azidomethyl)benzoic acid was prepared aspreviously described in Yoshida, S.; Misawa, Y.; Hosoya, T. Eur. J. Org.Chem., 2014, 19, 3991-3995. Rotary evaporation was performed under 30torr with a bath temperature below 40° C. Analytical LC-MS data wereobtained on a Waters Acquity UPLC system equipped with an Acquity BEH1.7 μm C₁₈ column (2.1×50 mm) and an elution gradient of 90:10 A:B to40:60 A:B over 2.3 min, where A=0.1% formic acid in water and B=0.1%formic acid in acetonitrile and with a flow rate of 0.80 mL min⁻¹.Column chromatography was performed on a Teledyne Isco Combiflash Rf+system using pre-packed RediSep Rf+ Gold silica gel (Teledyne Isco) or40-60 μm spherical C₁₈ silica gel columns (Agela). NMR spectra wereobtained on a Bruker 400 MHz spectrometer; chemical shifts arereferenced to the residual mono-¹H-isotopomer of the solvent:CHD₂OD=3.31 ppm; CD₃SOCD₂H=2.49 ppm; CHCl₃=7.26 ppm.

Compound 2: To a solution of MeOH (4 mL) and H₂O (1 mL) at roomtemperature was added 1 (100 mg, 242 μmol, 1eq.),2-[2-(2-azidoethoxy)ethoxy]ethylamine (42 mg, 242 μmol, 1.0 eq.),CuSO₄.5H₂O (60 mg, 242 μmol, 1.0 eq.) and sodium ascorbate (96 mg, 483μmol, 2.0 eq.). The mixture was stirred at 20° C. for 0.5 h. The mixturewas diluted with a saturated aqueous solution of NaHCO₃ (30 mL), thenthe mixture was extracted with EtOAc (3×50 mL). The combined extractswere washed with saturated aqueous NaCl solution, then were dried overNa₂SO₄. The solids were filtered and the filtrate was concentrated underreduced pressure to afford the crude product as a yellow solid. Theresidue was purified by preparatory HPLC using a Phenomenex Synergi C₁₈column (150×25×10 μm), eluting with a gradient of 10-30% CH₃CN in watercontaining 0.05% HCl to afford 2 as yellow solid (HCl salt, 65 mg, 43%yield). LCMS: t_(R): 1.749 min; (M+H)=588.2. ¹H NMR (400 MHz,METHANOL-d₄) ppm=9.12 (br s, 2H), 8.21 (br d, J=17.1 Hz, 3H), 7.76 (dd,J=6.0, 8.7 Hz, 1H), 7.42 (dd, J=2.4, 8.6 Hz, 1H), 7.26 (dt, J=2.6, 8.3Hz, 1H), 6.42 (s, 1H), 5.02-4.93 (m, 2H), 4.84 (s, 2H), 4.65 (t, J=5.0Hz, 2H), 3.94 (t, J=5.0 Hz, 2H), 3.75-3.55 (m, 9H), 3.10 (t, J=4.8 Hz,2H).

General procedure A—HATU-mediated acid-amine coupling reactions: To astirring solution of carboxylic acid (1.2 eq.) in DMF (0.05 M) at roomtemperature was added HATU (2.0 eq.), N,N-diisopropylethylamine (4.0eq.), and primary amine (1 eq.). The resulting solution was incubated atroom temperature for 2-16 h, then the reaction mixture was loadeddirectly onto a pre-packed C₁₈-silica gel column for purification.Fractions containing the desired product were combined, frozen at −78°C. (acetone/CO₂), and lyophilized to afford the final photoprobecompounds as solids.

Compound 3: Compound 3 was prepared according to General Procedure Aabove from 2 (30 mg, 51 μmol) and 4-benzoylbenzoic acid. The crudeproduct mixture was purified by reverse-phase chromatography overC₁₈-silica gel, eluting with 0-100% CH₃CN in water containing 0.1%formic acid. Probe 3 was isolated as a light tan solid (formate salt, 39mg, 83% yield). LC-MS: t_(R): 1.49 min; [M+H]⁺ 796.2.

Compound 4: Compound 4 was prepared according to General Procedure Aabove from 2 (30 mg, 51 μmol) and4-[3-(trifluoromethyl)-3H-diazirin-3-yl]benzoic acid. The crude productmixture was purified by reverse-phase chromatography over C₁₈-silicagel, eluting with 0-100% CH₃CN in water containing 0.1% formic acid.Compound 4 was isolated as a bright yellow solid (formate salt, 19 mg,44% yield). LC-MS: t_(R): 1.56 min; [M+H]⁺ 800.2.

Compound 5: Compound 5 was prepared according to General Procedure Aabove from 2 (50 mg, 85 μmol) and 4-azidobenzoic acid (as a 0.2 Msolution in methyl tent-butyl ether). After stirring at room temperaturefor 3 h, the crude product mixture was partially concentrated to removemethyl tent-butyl ether, then the resulting product solution (in DMF)was purified by reverse-phase chromatography over C₁₈-silica gel,eluting with 0-100% CH₃CN in water containing 0.1% formic acid. Compound5 was isolated as a bright yellow solid (formate salt, 32 mg, 49%yield). LC-MS: t_(R): 1.45 min; [M+H]⁺ 733.2.

Compound 6: To a stirring solution of 2 (30 mg, 51 μmol, 1 eq.) in DMF(2.0 mL) at room temperature was added N,N-diisopropylethylamine (27 μL,153 μmol, 3.0 eq.) and 2,5-dioxopyrrolidin-1-yl3-(3-methyl-3H-diazirin-3-yl)propanoate (12 mg, 54 μmol, 1.05 eq.). Theresulting bright yellow reaction mixture was allowed to stir at roomtemperature for 2 h, then was purified immediately by flash columnchromatography over C₁₈-silica gel, eluting with 0-60% CH₃CN in watercontaining 0.1% formic acid. Fractions containing the desired productwere concentrated under reduced pressure to remove CH₃CN, then werefrozen at −78° C. and lyophilized to afford the desired product 6 as abright yellow solid (formate salt, 16.0 mg, 42% yield). LC-MS: t_(R):1.40 min; [M+H]⁺ 698.3.

Compound 7: To a stirring suspension of 1 (321 mg, 0.78 mmol, 1 eq.) int-BuOH (4.0 mL) and water (4.0 mL) was added 3-azidopropylamine (93 mg,0.93 mmol, 1.2 eq.) and CuSO₄.5H₂O (15 mg, 62 μmol, 0.08 eq.). To theresulting suspension was added a solution of sodium ascorbate (46 mg,0.23 mmol, 0.30 eq.) in water (1.0 mL). The resulting suspension wasallowed to stir vigorously at room temperature for 2 h, then wasconcentrated under reduced pressure to remove t-BuOH. The crude productsolution that remained was directly purified by flash columnchromatography over C₁₈-silica gel, eluting with 0-30% CH₃CN in watercontaining 0.1% NH₃. Fractions containing the desired product werefrozen at −78° C. and lyophilized to afford compound 7 as a brightyellow solid (305 mg, 77% yield). LCMS: t_(R): 1.19 min; [M+H]⁺ 514.2.

Compound 8: To a stirring solution of 7 (30 mg, 58 μmol, 1 eq.) in DMF(2.0 mL) at room temperature was added N,N-diisopropylethylamine (41 233μmol, 4.0 eq.) and 2,5-dioxopyrrolidin-1-yl3-(3-methyl-3H-diazirin-3-yl)propanoate (14 mg, 64 μmol, 1.10 eq.). Theresulting bright yellow reaction mixture was allowed to stir at roomtemperature for 2 h, then was purified immediately by flash columnchromatography over C₁₈-silica gel, eluting with 0-100% CH₃CN in watercontaining 0.1% formic acid. Fractions containing the desired productwere concentrated under reduced pressure to remove CH₃CN, then werefrozen at −78° C. and lyophilized to afford the desired product as abright yellow solid (formate salt, 17.0 mg, 44% yield). LC-MS: t_(R):1.40 min; [M+H]⁺ 624.2.

Compound 9: To a stirring suspension of4-[3-(trifluoromethyl)-3H-diazirin-3-yl]benzoic acid (27 mg, 116 μmol,1.2 eq.) in CH₂Cl₂ (2.0 mL) at room temperature was added DMF (ca. 10μL) and a 2.0 M solution of oxalyl chloride in CH₂Cl₂ (49 98 μmol, 1.0eq.). The resulting clear, colorless mixture was allowed to stir at roomtemperature for 1 h, then 7 (50 mg, 97 μmol, 1 eq.) andN,N-diisopropylethylamine (68 0.39 mmol, 4.0 eq.) were added. Themixture was allowed to stir at room temperature for 3 h, then wasconcentrated under reduced pressure. The crude product was purified byreverse-phase flash column chromatography on C₁₈-silica gel, elutingwith 0-100% CH₃CN in water containing 0.1% formic acid. Fractionscontaining the desired product were combined and partially evaporated,then were frozen at −78° C. and lyophilized to afford the desiredproduct as a yellow solid (formate salt, 32 mg, 47% yield). LC-MS:t_(R): 1.57 min; [M+H]⁺ 726.0.

General Procedure B—Three component coupling of an amino acid,carboxylic acid NHS ester, and an amine: To a suspension of amino acid(1 eq.) in DMF (2.0 mL) at room temperature was addedN,N-diisopropylethylamine (4.0 eq.) and carboxylic acidN-hydroxysuccinimidyl ester (1.05 eq.). The resulting suspension wasallowed to stir at room temperature for 12-48 h. Once formation of theamide was complete (as determined by LC-MS analysis),1-[Bis(dimethylamino)methylene] -triazolo[4,5-b]pyridinium 3-oxidhexafluorophosphate (HATU) (2.0 eq.) and amine (1.2 eq.) were added andthe resulting bright yellow mixture was allowed to stir at roomtemperature for 3 h. The mixture was directly purified by columnchromatography over C₁₈ silica gel. Fractions containing the desiredproduct were combined and partially evaporated to remove CH₃CN, thenwere frozen at −78° C. and lyophilized to afford the desired products assolids.

Compound 10: Compound 10 was prepared according to General Procedure Babove from L-photoleucine (25 mg, 0.17 mmol, 1 eq.), biotinN-hydroxysuccinimidyl ester (62 mg, 0.18 mmol, 1.05 eq.), and 2 (122 mg,0.21 mmol, 1.2 eq.). The mixture was directly purified by columnchromatography over C₁₈ silica gel, eluting with 0-100% CH₃CN in watercontaining 0.1% formic acid. Fractions containing the desired productwere combined and partially evaporated to remove CH₃CN, then were frozenat −78° C. and lyophilized to afford the desired product as a yellowsolid (formate salt, 97 mg, 57% yield). LC-MS: t_(R): 1.35 min; [M+H]⁺939.3.

Compound 11: Compound 11 was prepared according to General Procedure Babove from N^(α)-tert-butoxycarbonyl-L-lysine (50 mg, 0.20 mmol, 1 eq.),2,5-dioxopyrrolidin-1-yl 3-(3-methyl-3H-diazirin-3-yl)propanoate (48 mg,0.21 mmol, 1.05 eq.), and 2 (142 mg, 0.24 mmol, 1.2 eq.). The mixturewas directly purified by column chromatography over C₁₈ silica gel,eluting with 0-50% CH₃CN in water containing 0.1% formic acid. Fractionscontaining the desired product were combined and partially evaporated toremove CH₃CN, then were frozen at −78° C. and lyophilized to afford thedesired product as a yellow solid (formate salt, 120 mg, 61% yield).LC-MS: t_(R): 1.46 min; [M+H]⁺ 926.4.

Compound 12: Compound 12 was prepared according to General Procedure Babove from N^(α)-tert-butoxycarbonyl-L-lysine (50 mg, 0.20 mmol, 1 eq.),biotin N-hydroxysuccinimidyl ester (72 mg, 0.21 mmol, 1.05 eq.), and 2(142 mg, 0.24 mmol, 1.2 eq.). The mixture was directly purified bycolumn chromatography over C₁₈ silica gel, eluting with 0-50% CH₃CN inwater containing 0.1% formic acid. Fractions containing the desiredproduct were combined and partially evaporated to remove CH₃CN, thenwere frozen at −78° C. and lyophilized to afford the desired product asa yellow solid (formate salt, 105 mg, 48% yield). LC-MS: t_(R): 1.38min; [M+H]⁺ 1042.4.

Compound 13: A stirring solution of 11 (40 mg, 41 μmol, 1 eq.) in CH₂Cl₂(1.0 mL) at 0° C. was treated dropwise with neat trifluoroacetic acid(250 μL). The resulting mixture was allowed to warm to room temperature,then was allowed to stir at room temperature for 15 min. The mixture wasconcentrated to dryness under reduced pressure to afford the crudeprimary amine. The crude amine was resuspended in DMF (1.0 mL), then wastreated with N,N-diisopropylethylamine (72 μL, 0.41 mmol, 10.0 eq.),biotin, (15 mg, 62 μmol, 1.5 eq.), and HATU (31 mg, 82 μmol, 2.0 eq.).The resulting bright yellow mixture was maintained at room temperaturefor 2 h, then was immediately loaded onto a C₁₈-silica gel column,eluting with 0-70% CH₃CN in water containing 0.1% formic acid).Fractions containing the desired product were combined and partiallyevaporated under reduced pressure to remove CH₃CN, then were frozen andlyophilized to afford the desired product as a yellow solid (formatesalt, 27 mg, 60% yield). LC-MS: t_(R): 1.38 min; [M+H]⁺ 1052.4.

Compound 14: A stirring solution of 12 (40 mg, 37 μmol, 1 eq.) in CH₂Cl₂(1.0 mL) at 0° C. was treated dropwise with neat trifluoroacetic acid(250 The resulting mixture was allowed to warm to room temperature, thenwas allowed to stir at room temperature for 55 min. The mixture wasconcentrated to dryness under reduced pressure to afford the crudeprimary amine. The crude amine was resuspended in DMF (1.0 mL), then wastreated with N,N-diisopropylethylamine (64 μL, 0.37 mmol, 10.0 eq.), and2,5-dioxopyrrolidin-1-yl 3-(3-methyl-3H-diazirin-3-yl)propanoate (10 mg,44 μmol, 1.2 eq.). The resulting bright yellow mixture was maintained atroom temperature for 16 h, then was immediately loaded onto a C₁₈-silicagel column, eluting with 0-70% CH₃CN in water containing 0.1% formicacid). Fractions containing the desired product were combined andpartially evaporated under reduced pressure to remove CH₃CN, then werefrozen and lyophilized to afford the desired product as a yellow solid(formate salt, 22 mg, 54% yield). LC-MS: t_(R): 1.37 min; [M+H]⁺ 1052.4.

Compound 15: Compound 15 was prepared according to General Procedure Babove using N^(ε)-tert-butoxycarbonyl-L-lysine (175 mg, 0.71 mmol, 1eq.), biotin N-hydroxysuccinimidyl ester (252 mg, 0.74 mmol, 1.05 eq.),and 2 (500 mg, 0.85 mmol, 1.2 eq.). Following completion of the reaction(as determined by LC-MS analysis), the reaction mixture was diluted withEtOAc (150 mL) and was washed with 4×40 mL portions of water. Theorganic phase was dried over Na₂SO₄, the solids filtered, and thefiltrate was concentrated to afford the crude product as a yellow gum.The crude product was triturated once with diethyl ether : pentane (1:1,10 mL), then the resulting solid was dissolved in methanol (5 mL) andwas cooled to −50° C. Diethyl ether (20 mL) was added, then theresulting solid was collected by filtration to afford 15 as a yellowsolid (380 mg, 43% yield). LC-MS: t_(R): 1.40 min; [M+H]⁺ 1042.1.

Compound 16: Compound 16 was prepared analogously to compound 15, withthe exception that N^(ε)-tert-butoxycarbonyl-D-lysine (900 mg, 1.90mmol, 1 eq.) was used in place of N^(ε)-tert-butoxycarbonyl-L-lysine asthe starting amino acid. Compound 16 was obtained as a yellow solid(1.03 g, 52% yield). LC-MS: t_(R): 1.40 min; [M+H]⁺ 1042.1.

Compound 17: A solution of 15 (55 mg, 53 μmol, 1 eq.) in CH₂Cl₂ (1.0 mL)at 0° C. was treated with trifluoroacetic acid (0.25 mL). The resultingmixture was allowed to warm to room temperature over 15 minutes. Afterthis time the mixture was concentrated to dryness under reducedpressure. The resulting crude amine was dissolved in DMF (2.0 mL), thenwas treated with a 0.2 M solution of 4-azidobenzoic acid in methyltent-butyl ether (0.53 mL, 0.11 mmol, 2.0 eq.), HATU (40 mg, 0.11 mmol,2.0 eq.), and N,N-diisopropylethylamine (37 0.21 mmol, 4.0 eq.). Theresulting mixture was allowed to stir at room temperature overnight,then was partially concentrated to remove methyl tent-butyl ether. Theresulting product solution (in DMF) was directly purified by columnchromatography over C₁₈-silica gel, eluting with 0-100% CH₃CN in watercontaining 0.1% formic acid. Fractions containing the desired productwere combined and partially evaporated to remove CH₃CN, then were frozenat −78° C. and lyophilized to afford 17 as a yellow solid (formate salt,35 mg, 58% yield). LC-MS: t_(R): 1.41 min; [M+H]⁺ 1087.4.

Compound 18: A solution of 16 (55 mg, 53 μmol, 1 eq.) in CH₂Cl₂ (1.0 mL)at 0° C. was treated with trifluoroacetic acid (0.25 mL). The resultingmixture was allowed to warm to room temperature over 15 minutes. Afterthis time the mixture was concentrated to dryness under reducedpressure. The resulting crude amine was dissolved in DMF (2.0 mL), thenwas treated with a 0.2 M solution of 4-azidobenzoic acid in methyltent-butyl ether (0.53 mL, 0.11 mmol, 2.0 eq.), HATU (40 mg, 0.11 mmol,2.0 eq.), and N,N-diisopropylethylamine (37 μL, 0.21 mmol, 4.0 eq.). Theresulting mixture was allowed to stir at room temperature overnight,then was partially concentrated to remove methyl tent-butyl ether. Theresulting product solution (in DMF) was directly purified by columnchromatography over C₁₈-silica gel, eluting with 0-100% CH₃CN in watercontaining 0.1% formic acid. Fractions containing the desired productwere combined and partially evaporated to remove CH₃CN, then were frozenat −78° C. and lyophilized to afford 18 as a yellow solid (formate salt,38 mg, 63% yield). LC-MS: t_(R): 1.41 min; [M+H]⁺ 1087.4.

Compound 19: A solution of 15 (55 mg, 53 μmol, 1 eq.) in CH₂Cl₂ (1.0 mL)at 0° C. was treated with trifluoroacetic acid (0.25 mL). The resultingmixture was allowed to warm to room temperature over 15 minutes. Afterthis time the mixture was concentrated to dryness under reducedpressure. The resulting crude amine was dissolved in DMF (2.0 mL), thenwas treated with 4-[3-(trifluoromethyl)-3H-diazirin-3-yl]benzoic acid(24 mg, 0.11 mmol, 2.0 eq.), HATU (40 mg, 0.11 mmol, 2.0 eq.), andN,N-diisopropylethylamine (37 μL, 0.21 mmol, 4.0 eq.). The resultingmixture was allowed to stir at room temperature overnight, then theresulting product solution (in DMF) was directly purified by columnchromatography over C₁₈-silica gel, eluting with 0-100% CH₃CN in watercontaining 0.1% formic acid. Fractions containing the desired productwere combined and partially evaporated to remove CH₃CN, then were frozenat −78° C. and lyophilized to afford 19 as a yellow solid (formate salt,15 mg, 24% yield). LC-MS: tR: 1.48 min; [M+H]⁺ 1155.6.

Compound 20: A solution of 15 (55 mg, 53 μmol, 1 eq.) in CH₂Cl₂ (1.0 mL)at 0° C. was treated with trifluoroacetic acid (0.25 mL). The resultingmixture was allowed to warm to room temperature over 15 minutes. Afterthis time the mixture was concentrated to dryness under reducedpressure. The resulting crude amine was dissolved in DMF (2.0 mL), thenwas treated with a 4-benzoylbenzoic acid (24 mg, 0.11 mmol, 2.0 eq.),HATU (40 mg, 0.11 mmol, 2.0 eq.), and N,N-diisopropylethylamine (37 μL,0.21 mmol, 4.0 eq.). The resulting mixture was allowed to stir at roomtemperature overnight, then the resulting product solution (in DMF) wasdirectly purified by column chromatography over C₁₈-silica gel, elutingwith 0-100% CH₃CN in water containing 0.1% formic acid. Fractionscontaining the desired product were combined and partially evaporated toremove CH₃CN, then were frozen at −78° C. and lyophilized to afford 20as a yellow solid (formate salt, 32 mg, 52% yield). LC-MS: t_(R): 1.43min; [M+H]⁺ 1151.7.

Compound 21: Compound 21 was prepared according to General Procedure Aabove from 2 (37 mg, 63 μmol) and 4-azido-2,3,5,6-tetrafluorobenzoicacid. After stirring at room temperature for 3 h, the crude productmixture was purified by reverse-phase chromatography over C₁₈-silicagel, eluting with 0-100% CH₃CN in water containing 0.1% formic acid.Compound 21 was isolated as a bright yellow solid (formate salt, 26 mg,52% yield). LC-MS: t_(R): 1.51 min; [M+H]⁺ 806.6.

Compound 22: Compound 22 was prepared according to General Procedure Aabove from 2 (37 mg, 63 μmol) and 3-azido—S—(azidomethyl)benzoic acid.After stirring at room temperature for 3 h, the crude product mixturewas purified by reverse-phase chromatography over C₁₈-silica gel,eluting with 0-100% CH₃CN in water containing 0.1% formic acid. Compound22 was isolated as a bright yellow solid (formate salt, 26 mg, 52%yield). LC-MS: t_(R): 1.51 min; [M+H]⁺ 789.5.

Example 4 SFC Separation of I-1 (ARK-139) Enantiomers and Determinationof Absolute Stereochemistry of Active Isomer

Racemic I-1 (ARK-139) was subjected to SFC chiral separation (ChiralPakA D column, isocratic elution of 70%A/30%B, phase A for supercriticalCO₂, phase B for MeOH, total flowrate of 60 g/min, cycle time 3 min),and two peaks were separated and collected.

Separation of the two enantiomers of I-1 allows preparation ofnon-racemic versions of each of the compounds of Table 5 and Example 3and other HAP compounds disclosed herein. In some embodiments, thepresent invention accordingly provides such compounds that areenantioenriched at the HAP stereocenter.

(R)-methyl4-(2-chloro-4-fluorophenyl)-6-(((1-(2-(2-(2-hydroxyethoxy)ethoxy)ethyl)-1H-1,2,3-triazol-4-yl)methoxy)methyl)-2-(pyridin-4-yl)-1,4-dihydropyrimidine-5-carboxylate(I-1b above). Yellow oil. ¹H NMR: (400 MHz, CDCl₃) δ 8.68 (q, J=1.6, 3.2Hz, 2 H), 8.54 (br s, 1H), 7.87 (s, 1H), 7.70 (q, J=1.6, 3.2 Hz, 2H),7.31 (dd, J=6.0, 2.4 Hz, 1H), 7.13 (dd, J=2.4, 6.0 Hz, 1H), 6.95-6.90(dt, J=4.2, 8.4 Hz, 1H), 6.21 (s, 1H), 4.98 (d, J=1.0, 2H), 4.83 (s,2H), 4.59 (t, J=4.8 Hz, 2H), 3.90 (t, J=4.8 Hz, 2H), 3.71 (t, J=4.8 Hz,2H), 3.65-3.60 (m, 7H), 3.56 (t, t, J=4.8 Hz, 1H), 2.70 (br s, 1H).LCMS, calcd C₂₇H₃₀ClFN₆O₆ (M+H)=589.02, found=589.4. Retention time inchiral LCMS: 1.74 min, Optical rotation: [α ]D²⁵+57.4 (c 0.7, MeOH).

(S)-methyl4-(2-chloro-4-fluorophenyl)-6-(((1-(2-(2-(2-hydroxyethoxy)ethoxy)ethyl)-1H-1,2,3-triazol-4-yl)methoxy)methyl)-2-(pyridin-4-yl)-1,4-dihydropyrimidine-5-carboxylate(I-1a above). Yellow oil. ¹H NMR: (400 MHz, CDCl₃) δ 8.68 (q, J=1.6, 3.2Hz, 2 H), 8.54 (br s, 1H), 7.87 (s, 1H), 7.70 (q, J=1.6, 3.2 Hz, 2H),7.31 (dd, J=6.0, 2.4 Hz, 1H), 7.13 (dd, J=2.4, 6.0 Hz, 1H), 6.95-6.90(dt, J=4.2, 8.4 Hz, 1H), 6.21 (s, 1H), 4.98 (s, 2H), 4.83 (s, 2H), 4.59(t, J=4.8 Hz, 2H), 3.90 (t, J=4.8 Hz, 2H), 3.71 (t, J=4.8 Hz, 2H),3.65-3.60 (m, 7H), 3.56 (t, t, J=4.8 Hz, 1H), 2.62 (br s, 1H). LCMS,calcd C₂₇H₃₀ClFN₆O₆ (M+H)=589.02, found=589.4. Retention time in chiralLCMS: 1.93 min, Optical rotation: [α]_(D) ²⁵−60.7 (c 0.7, MeOH).

SFC Separation Conditions Instrument Waters 80Q SFC Column ChiralPak ADcolumn, 250 × 25 mm I.D., 10um particle size; Mobile Phase Phase A forSupercritical CO₂ Phase B for Methanol (neutral)) Isocratic elution 30%Phase B (70% Phase A) Total flow rate 60 g/min Cycle time 3 min BackPressure 100 bar to keep the CO₂ in Supercritical flow Detector UV 220nm Sample preparation Material (about 80 mg) was dissolved in 25 mL MeOHInjection 1 mL

Further experiments (SPR) showed that ARK-702 (I-1a) did not bind at 10uM to Aptamer 21. On the other hand, ARK-701 (I-1b) did bind and istherefore the sole active isomer. Absolute stereochemistry wasdetermined as shown below and using SFC to confirm.

Example 5. Procedure for SEC/MS Analyses

Online SEC-LCMS has been used to study the binding to Aptamer 21 RNAagainst I-1 (ARK-139).

The RNA concentration was 1 μM and the ligand concentration ranged from0.1 μM to 10 μM in an appropriate buffer (TRIS-HCl 20 mM pH 8.0, MgCl₂ 3mM, KCl 100 mM).

The RNA/ligand mixtures were incubated at room temperature for 20minutes in a 96-well plate format, then this plate was loaded into anautosampler linked to the chromatography system fitted with a reusableSEC column for rapid separation of target/ligand complexes from unboundcomponents. RNA/ligand complexes in SEC eluent were monitored by UVdetection, and an automated valving system directed the RNA peak to areverse phase chromatography column for dissociation, desalting, andelution of any ligands into an ESI-MS system for identification.

All liquid chromatographic components were HP1200 modules. The massspectrometer was the Waters LCT premier instrument operated in positiveelectrospray (ES+) TOF-MS mode. The mass range acquired was 80-1000 m/zin 0.25 s. The SEC column was 50×4.6 mm polyhydroxyethyl column. The SECmobile phase was 50 mM phosphate buffer with 200 mM NaCl, pH=7.0. The LCcolumn was a 2.1×50 mm C18 Phenomenex column. The gradient LC mobilephase A was 0.1% formic acid in water and B was acetonitrile/water with0.1% formic acid. The run time was 7.9 min.

For more information on SEC/LCMS, see, e.g., Blom, K. F. et al., J.Comb. Chem. 1999, 1, 82-90.

Results

Binding of I-1 to Aptamer 21 was measured. SEC/LCMS conditions for thisexperiment were: [I-1]=5 uM, [RNA]=1 uM, Buffer=Tris-HCl 20 mM, KCl 100mM, 3 mM MgCl₂.

TABLE 6 Binding of I-1 to Aptamer 21 ARK-000139 Peak area Peak area conc(μM) SEC-LCMS LCMS % of binding 0.1 26.81 36.99 72.5 0.5 75.34 206.3336.5 1 151.55 451.51 33.6 3 372.39 1665.87 22.4 10 471.84 5305.54 8.9

The experiment was duplicated and showed good reproducibility betweenthe 2 experiments. The start of saturation was between 1 and 3 μM.SEC/LCMS was also used to measure I-1 binding to Aptamer 21-E.Consistent with SPR data and the published literature, I-1 does not bindAptamer 21-E. SEC/LCMS represents a promising homogeneous method forassessing affinity.

Example 6 PEARL-seq Photoprobe Assay

General Methods

Sequences

The following sequences were employed in the assays described herein.

TABLE 7 Nucleic Acid Sequences Name Sequence PEARLv2_RTCTTTCCCTACACGACGCTCTTCCGATCTTAGATCATTGATGG TGCCTACAG (SEQ ID NO: 26)PEARLv2_2nd_adapter AGATCGGAAGAGCACACGTCTGAACTCCAGTCAC (SEQ ID NO: 27)PEARLv2_for_pri CAAGCAGAAGACGGCATACGAGAT <index> (where <index>GTGACTGGAGTTCAGACGTGTGCTC (SEQ ID NO: 28) refers to the 6 bp Illuminaindex) PEARLv2_rev_priAATGATACGGCGACCACCGAGATCTACACTCTTTCCCTACACGACGCTCTTCCG ATCT (SEQ ID NO:29) PEARLv3_1st_linker/5Phos/rArUrArUrArGrGrNrNrNrNrNrNrArGrArUrCrGrGrArArGrArGrCrArCrArCrGrUr(where rN refers CrUrGrArArCrUrC/3SpC3/ (SEQ ID NO: 30) to a randommixture of the A, G, C and U RNA residues) PEARLv3_2nd_adapter/5Phos/AGATCGGAAGAGCGTCGTGTAGGGAAAGAGTGT/3SpC3/(SEQ ID NO: 31)PEARLv3_RT GAGTTCAGACGTGTGCTCTTCCGATCT (SEQ ID NO: 32) PEARLv3_for_priAATGATACGGCGACCACCGAGATCTACAC <i5> ACACTCTTTCCCTACACGAC (where <i5> (SEQID NO: 33) refers to the 6 bp Illumina i5 index) PEARLv3_rev_priCAAGCAGAAGACGGCATACGAGAT <i7> GTGACTGGAGTTCAGACGTGTGCTC (where <i7> (SEQID NO: 34) refers to the 6 bp Illumina i7 index)

TABLE 8 Illumina Index Sequences Index ID Sequence 1 CGTGAT 2 ACATCG 3GCCTAA 4 TGGTCA 5 CACTGT 6 ATTGGC 7 GATCTG 8 TCAAGT 9 CTGATC 10 AAGCTA11 GTAGCC 12 TACAAG 13 TTGACT 14 GGAACT 15 TGACAT 16 GGACGG 18 GCGGAC 19TTTCAC 20 GGCCAC 21 CGAAAC 22 CGTACG 23 CCACTC 25 ATCAGT 27 AGGAAT

Folding RNA

A solution of RNA at 2 to 5 μM in nuclease-free water was heated to 95°C. for 3 min and then cooled on ice for 2 min. This solution was dilutedwith ½ volume of 3× RNA folding buffer (60 mM TrisHCl pH 8, 300 mM KCl,9 mM MgCl₂) and incubated at 37° C. for 20 min. Folding was carried outimmediately before use of the RNA in each experiment. In cases where amixture of RNA molecules was used in vitro the RNAs were foldedseparately and then combined prior to the probing experiment.

Reverse Transcription Drop-Off Gel Assay

Cross-Linking

Folded RNA (1 μM) was incubated with the photoaffinity probe (10 μM) intotal 25 μL of buffer (20 mM TrisHCl pH 8, 100 mM KCl, 3 mM MgCl₂) with2.5% DMSO for 30 min at 37° C. to allow binding to come to equilibrium.The sample was then irradiated with long wave UV light (˜365 nm) for 30min in a UV crosslinker (Fisher Scientific).

Reverse Transcription

A 3.75 μL aliquot of 10 μM reverse transcription primer was added to thecross-linked RNA sample, which was then incubated for 5 min at 65° C.and then cooled on ice. The sample was then diluted to a final volume of60 μL and final buffer concentration of 1× Protoscript-II buffer (NewEngland Biolabs), 0.5 mM dNTPs, 10 mM DTT, 0.4 U/μL RNase Inhibitor (NewEngland Biolabs), and 10 U/μL Protoscript-II (New England Biolabs). Thereaction was incubated at 45° C. for 2 h, 65° C. for 20 min, and then 4°C.

Isolation of cDNA

The RNA was hydrolyzed by the addition of 4.8 μL of 2.5 M NaOH andheating at 95° C. for 5 min. The reaction was quenched by the additionof 0.9 μL of acetic acid. The cDNA was precipitated by the addition of6.6 μL of 3 M sodium acetate pH 5 and 181 μL ethanol, cooling to −80° C.for 1 h, and then centrifuging at 20,500×g at 4° C. for 30 min. The cDNApellet was washed twice with 500 μL of 70% ethanol and then air driedfor 5 min.

Polyacrylamide Gel Analysis

The cDNA pellet was resuspended in 12 μL of 1× TBE-urea sample loadingbuffer (Bio-Rad) and heated to 95° C. for 5 min. The sample was then runon a pre-cast 8.6×6.7 cm TBE-urea 10% PAGE gel (Bio-Rad) at 120 V untilthe lower bromophenol blue dye reached the bottom of the gel. The gelwas stained with 1× SYBR-gold (Invitrogen) in 1× TBE buffer at roomtemperature for 20 min covered from light. The gel fluorescence wasimaged on an Azure c600 instrument.

LC-MS Analysis of Cross-Linked RNA

Generating Cross-Linked RNA

Folded RNA (1.33 μM) was incubated with or without the photoaffinityprobe (20 μM) in total 100 μL of buffer (20 mM TrisHCl pH 8, 100 mM KCl,3 mM MgCl₂) with 2% DMSO for 30 min at 37° C. to allow binding to cometo equilibrium. The sample was then irradiated with long wave UV light(˜365 nm) for 30 min in a UV crosslinker (Fisher Scientific).

The RNA was then precipitated by adding 10 μL of 3 M sodium acetate pH 5and 275 μL ethanol, cooling to −80° C. for 1 h, and then centrifuging at20,500×g at 4° C. for 30 min. The RNA pellet was washed with 500 μL of70% ethanol, air dried for 5 min, and then resuspended in 120 μL ofwater.

LC-MS Analysis

50 μL of RNA sample was injected onto Clarity 2.6 μm Oligo X-T column(50 * 2.1 mm, 60° C.), and the gradient and flowrate were as follows:95% A/5% B to 75% A/25% B over 5 min, flowrate: 400 μL/min; 75% A/25% Bto 30% A/70% B over 1 min, flowrate: 400 μL/min; 100% D over 1 min,flowrate: 500 μL/min; 95% A/5% B over 2 min, flowrate: 500 μL/min (A: 1%HFIPA (hexafluoroisopropyl alcohol), 0.1% DIEA (diisopropylethylamine),1 μM EDTA (ethylenediamine tetraacetic acid) in H2O; B: 0.075% HFIPA,0.0375% DIEA, 1 μM EDTA in 65/35 MeCN/H₂O; D: 40/40/20% MeOH/MeCN/H20);The LCMS instrument was a Thermo Finnigan LTQ, and ProMass deconvolutionsoftware coupled with Xcaliber were used for all data processing.

Next Generation Sequencing Analysis of ARK-547 Cross-Linked RNA

Generating Crosslinked RNA

A 9.5 μL sample of folded RNA (2.6 μM) in buffer (20 mM TrisHCl pH 8,100 mM KCl, 3 mM MgCl₂) was added to a 0.5 μL aliquot of 1 mM ARK-547 inDMSO. The reaction was incubated for 10 min at 37° C., irradiated withlong wave UV light (˜365 nm) for 30 min in a UV crosslinker (FisherScientific), and then kept on ice.

Linker Ligation

The samples of cross-linked RNA were diluted to a final volume of 20 μLand final reaction conditions of 1×T4 RNA ligase buffer (New EnglandBiolabs), 5 U/μL T4 RNA ligase 2, truncated KQ (New England Biolabs),16.5% PEG−8000, and 0.5 μM universal miRNA cloning linker (New EnglandBiolabs). The reaction was incubated in a thermal cycler for 2.5 hcycling between 5 min at 16° C. and 3 min at 25° C. The RNA was thenpurified using Agencourt AMPure XP beads (Beckman Coulter) using thestandard protocol from the manufacturer. The RNA was eluted with 20 μLof nuclease-free water.

Reverse Transcription

A 10 μL aliquot of the eluted RNA sample was mixed with a 1 μL aliquotof 2 μM PEARLv2_RT primer, heated to 65° C. for 5 min, and then cooledon ice. An 8 μL sample of 2.5× mutagenic reverse transcription buffer(125 mM TrisHCl pH 8, 187.5 mM KCl, 25 mM DTT, 1.25 mM dNTPs) was addedto the sample and it was heated to 42° C. for 2 min, followed byaddition of 1 μL of SuperScript II enzyme (Thermo), and then incubationat 42° C. for 3 h and 70° C. for 15 min.

To remove excess primer, the sample was mixed with 4.5 μL of ExoSAP-IT,incubated at 37° C. for 15 min, and then quenched with 1 μL of 0.5 MEDTA pH 8. The RNA was then degraded by adding 2.08 μL of 2.5 M NaOH,incubating at 95° C. for 5 min, and quenching with 3.25 μL of 10% aceticacid. The remaining cDNA was purified by Agencourt AMPure XP beads(Beckman Coulter) using the standard protocol from the manufacturer andeluted in 30 μL of nuclease-free water. The concentration was determinedby absorbance at 260 nm.

Second Adaptor Ligation

Second adaptor ligation was carried out using the CircLigase ssDNAligase system (Epicentre). A 0.8 pmol aliquot of purified cDNA wasbrought to a final volume of 20 μL and final concentration of 83.5 μMPEARLv2_2nd_adapter oligo, 1× CircLigase buffer, 50 μM ATP, 2.5 mMMnC12, and 5 U/μL enzyme. The reaction was incubated at 60° C. for 2 hand then 80° C. for 10 min. The adaptor-ligated cDNA was purified byAgencourt AMPure XP beads (Beckman Coulter) using the standard protocolfrom the manufacturer and eluted in 30 μL of nuclease-free water.

Polymerase Chain Reaction

The adaptor-ligated cDNA was PCR amplified using Q5 high-fidelity DNApolymerase (New England Biolabs) to install the Illumina adaptorsequences. A 5 μL aliquot of the adaptor-ligated cDNA was brought to afinal volume of 50 μL and final concentration of 0.2 μM PEARLv2_for_ priprimer, 0.2 μM PEARLv2_rev_pri primer, and 1× Q5 master mix. Thepolymerase chain reaction was carried out with heating to 98° C. for 30seconds; 5 cycles of 98° C. for 10 seconds, 60° C. for 30 seconds, and72° C. for 30 seconds; 15 cycles of 98° C. for 10 seconds, and 72° C.for 30 seconds; 72° C. for 2 min. A different Illumina barcode wasinstalled in each PCR product via the forward primer. PCR products werepurified using Agencourt AMPure XP beads (Beckman Coulter) using thestandard protocol from the manufacturer and eluted in 30 μL ofnuclease-free water.

Next Generation Sequencing

The concentrations of different PCR products were measured using theDenovix dsDNA fluorescence quantitation kit (Denovix) and multiplexed atequal concentrations with a 20% PhiX spike-in. Sequencing was performedon an Illumina MiSeq with 150 bp paired-end reads using the standardmanufacturer protocol.

Capture of Aptamer 21 from a Defined Mixture of RNAs

Generating Crosslinked RNA

A sample of folded RNA was prepared containing 1 μM each of Myc_HP_PA,Aptamer 21, FMN, MYC_3WJ-HP_N3G, and PreQ1 RNAs in folding buffer (20 mMTrisHCl pH 8, 100 mM KCl, 3 mM MgCl₂). A 95 μL sample of this solutionwas added to a 5 μL aliquot of 0.2 mM ARK-670 (probe) or ARK-139(control) in DMSO. The reaction was incubated for 30 min at 37° C.,irradiated with long wave UV light (˜365 nm) for 30 min in a UVcrosslinker (Fisher Scientific), and then cooled on ice. The excessprobe and buffer was then removed by passing the sample through anIllustra MicroSpin G-25 spin column (GE Healthcare) according to themanufacturer's protocol.

Avidin Bead Capture

For each treatment, a 75 μL aliquot of the crosslinked RNA was mixedwith 0.75 μL of 10% Tween-20 and 0.45 μL of 0.5 M EDTA pH 8 solution. A50 μL aliquot of MyOne Streptavidin C1 Dynabead slurry (Thermo) wascaptured on a magnet, washed twice with 50 μL of 1× bind/wash buffer (20mM TrisHCl pH 7, 100 mM KCl, 0.1% Tween-20), and then resuspended in 50μL of the crosslinked RNA sample. The bead suspension was rotated atroom temperature for 60 min and then washed twice with 100 μL of 1×bind/wash solution. To elute the bound RNA, the beads were resuspendedin 50 μL of elution buffer (95% formamide, 20 mM EDTA), heated to 95° C.for 5 min, and then the supernatant was removed. The RNA was ethanolprecipitated by adding 50 μL of water, 2 uL of 5 mg/mL glycogen, 10 μL 3M NaOAc pH 5, and 250 μL ethanol, incubating at −80° C. for 1 h,centrifuging at 20,000g for 30 min, washing the pellet twice with 500 μLof 70% ethanol, air drying the pellet, and then resuspending the pelletin 16 μL of nuclease-free water.

Linker ligation

The samples of bead-eluted RNA were diluted to a final volume of 20 μLand final reaction conditions of 1× T4 RNA ligase buffer (New EnglandBiolabs), 5 U/μL T4 RNA ligase 2, truncated KQ (New England Biolabs),16.5% PEG−8000, and 0.5 μM universal miRNA cloning linker (New EnglandBiolabs). The reaction was incubated in a thermal cycler for 2.5 hcycling between 5 min at 16° C. and 3 min at 25° C. The RNA was thenpurified using Agencourt AMPure XP beads (Beckman Coulter) using thestandard protocol from the manufacturer. The RNA was eluted with 11 μLof nuclease-free water.

Reverse transcription with SuperScript III

To the 11 μL RNA sample from linker ligation was added 1 μL of 2 μMPEARLv2_RT primer and 1 μL of 10 mM dNTP mix. The sample was heated to65° C. for 5 min and then cooled on ice for 1 min. The sample was thenmixed with 4 μL of 5X first-strand buffer (Thermo), 1 μL of 0.1 M DTT, 1μL of RNaseOUT (Thermo), and 1 μL of SuperScript III enzyme (Thermo).The reaction was incubated at 55° C. for 45 min, 70° C. for 15 min, andthen cooled to 4° C.

To remove excess primer, the sample was mixed with 4.5 μL of ExoSAP-IT,incubated at 37° C. for 15 min, and then quenched with 1 μL of 0.5 MEDTA pH 8. The RNA was then degraded by adding 2.08 μL of 2.5 M NaOH,incubating at 95° C. for 5 min, and quenching with 3.25 μL of 10% aceticacid. The remaining cDNA was purified by Agencourt AMPure XP beads(Beckman Coulter) using the standard protocol from the manufacturer andeluted in 15 μL of nuclease-free water. The concentration was determinedby absorbance at 260 nm.

Second Adapter Ligation

Second adaptor ligation was carried out using the CircLigase ssDNAligase system (Epicentre). A 0.8 pmol aliquot of purified cDNA wasbrought to a final volume of 20 μL and final concentration of 83.5 μMPEARLv2_2nd adapter oligo, 1× CircLigase buffer, 50 μM ATP, 2.5 mMMnCl₂, and 5 U/μL enzyme. The reaction was incubated at 60° C. for 2 hand then 80° C. for 10 min. The adaptor-ligated cDNA was purified byAgencourt AMPure XP beads (Beckman Coulter) using the standard protocolfrom the manufacturer and eluted in 30 μL of nuclease-free water.

Polymerase Chain Reaction

The adaptor-ligated cDNA was PCR amplified using Q5 high-fidelity DNApolymerase (New England Biolabs) to install the Illumina adaptorsequences. A 5 μL aliquot of the adaptor-ligated cDNA was brought to afinal volume of 50 μL and final concentration of 0.2 μM PEARLv2_for_priprimer, 0.2 μM PEARLv2_rev_pri primer, and 1× Q5 master mix. Thepolymerase chain reaction was carried out with heating to 98° C. for 30seconds; 5 cycles of 98° C. for 10 seconds, 60° C. for 30 seconds, and72° C. for 30 seconds; 15 cycles of 98° C. for 10 seconds, and 72° C.for 30 seconds; 72° C. for 2 min. A different Illumina barcode wasinstalled in each PCR product via the forward primer. PCR products werepurified using Agencourt AMPure XP beads (Beckman Coulter) using thestandard protocol from the manufacturer and eluted in 30 μL ofnuclease-free water.

Next Generation Sequencing

The concentrations of different PCR products were measured using theDenovix dsDNA fluorescence quantitation kit (Denovix) and multiplexed atequal concentrations with a 20% PhiX spike-in. Sequencing was performedon an Illumina MiSeq with 150 bp paired-end reads using the standardmanufacturer protocol.

Capture of Aptamer 21 with Click-Biotinylated Probes

Generating Crosslinked and Click-Biotinylated RNA

A 50 μL sample of 1 μM folded Aptamer 21 or Aptamer 21-E solution infolding buffer (20 mM TrisHCl pH 8, 100 mM KCl, 3 mM MgCl₂) was added toa 0.5 μL aliquot of 0.5 mM ARK-729, ARK-2058, ARK-816, or ARK-2059 inDMSO or a DMSO-only control. The solution was incubated at 37° C. for 1h and then irradiated with long wave UV light (˜365 nm) for 30 min in aUV crosslinker (Fisher Scientific). To this solution was added 0.5 μL of10 mM DBCO-biotin (Click Chemistry Tools, cat. # A105) and 2 μL of 0.5 MEDTA pH 8 and then the solution was incubated at 65° C. for 2 h. The RNAwas ethanol precipitated by adding 35 μL of water, 2 uL of 5 mg/mLglycogen, 10 μL 3 M NaOAc pH 5, and 250 μL ethanol, incubating at −80°C. for 1 h, centrifuging at 20000×g for 30 min, washing the pellet twicewith 500 μL of 70% ethanol, and then air drying the pellet.

Streptavidin Bead Capture

The RNA pellet was redissolved in 50 μL of 1× bind/wash buffer (20 mMTrisHCl pH 7, 100 mM KCl, 0.1% Tween-20). A 50 μL aliquot of MyOneStreptavidin Cl Dynabead slurry (Thermo) was captured on a magnet,washed twice with 50 μL of 1× bind/wash buffer, and then resuspended in50 μL of the crosslinked RNA sample. The bead suspension was rotated atroom temperature for 30 min and then washed twice with 100 μL of 1×bind/wash solution.

On-bead Dephosphorylation

The magnetic beads with captured RNA were resuspended in a 50 μLsolution containing 1× FastAP buffer and 0.08 U/μL FastAP enzyme(Thermo) and the slurry was incubated at 37° C. for 15 min with 1200 rpmagitation. A 150 μL solution of 1× PNK buffer, 1 mM DTT, and 0.25 U/μLT4 PNK (New England Biolabs) was then added to the mixture and theslurry was incubated at 37° C. for 20 min with 1200 rpm agitation. Thebeads were then washed three times with 400 μL of 1× bind/wash solution.

First Linker Ligation

The beads were washed twice with 400 μL of linker wash buffer (50 mMTrisHCl pH 8, 5 mM MgCl₂) and then resuspended in a 27.5 μL ligationreaction mixture containing 2 μM of the PEARLv3_1st_linker oligo, 1× RNALigase 1 buffer, 1 mM ATP, 2.9% DMSO, 16% PEG8000, and 2.7 U/μL RNALigase 1 (New England Biolabs, cat # M0437). The slurry was incubated at22° C. for 75 min with 1200 rpm agitation and then the beads were washedtwice with 100 μL of 1× bind/wash buffer.

Reverse Transcription

The beads were washed twice with 200 μL of 1× first-strand buffer(Thermo) and then resuspended in a solution containing 14.75 μL water,1.25 μL of 10 mM dNTPs, and 0.25 μL of 10 μM PEARLv3_RT oligo. Theslurry was heated to 65° C. for 5 min, chilled on ice, and then asolution containing 5 μL of 5× first-strand buffer (Thermo), 1.25 μL of100 mM DTT, 1.25 μL of RNaseOUT (Thermo), and 1.25 μL of SuperScript III(Thermo) was added. The slurry was mixed, incubated at 50° C. for 50min, heated to 85° C. for 5 min, and then chilled on ice.

To elute the cDNA, the 2.5 μL of 2.5 M sodium hydroxide was added to theslurry and it was heated to 95° C. for 5 min, chilled on ice, and then3.6 μL of a 1.74 M solution of acetic acid was added to quench the pH.The supernatant was removed from the beads, brought to a final volume of50 μL with nuclease-free water, and then purified using Agencourt AMPureXP beads (Beckman Coulter) using the standard protocol from themanufacturer and eluted in 15 μL of nuclease-free water.

Second Adapter Ligation

A 14 μL aliquot of the AMPure-eluted cDNA was brought to 20 μL reactionmixture with a final concentration of 1X CircLigase buffer, 80 nMPEARLv3_2nd_adapter oligo, 50 μM ATP, 2.5 mM MnCl₂, and 5 U/μLCircLigase ssDNA ligase (EpiCentre) and incubated at 60° C. for 2 h andthen 80° C. for 10 min. The ligated cDNA was purified using AgencourtAMPure XP beads (Beckman Coulter) using the standard protocol from themanufacturer and eluted in 25 μL of nuclease-free water.

Polymerase Chain Reaction

The adaptor-ligated cDNA was PCR amplified using Q5 high-fidelity DNApolymerase (New England Biolabs) to install the Illumina adaptorsequences. A 5 μL aliquot of the adaptor-ligated cDNA was brought to afinal volume of 50 μL and final concentration of 0.2 μM PEARLv3_for_priprimer, 0.2 μM PEARLv3_rev_pri primer, and 1× Q5 master mix. Thepolymerase chain reaction was carried out with heating to 98° C. for 30seconds; 5 cycles of 98° C. for 10 seconds, 60° C. for 30 seconds, and72° C. for 30 seconds; 15 cycles of 98° C. for 10 seconds, and 72° C.for 30 seconds; 72° C. for 2 min. A different Illumina barcode wasinstalled in each PCR product via the forward primer. PCR products werepurified using Agencourt AMPure XP beads (Beckman Coulter) using thestandard protocol from the manufacturer and eluted in 30 μL ofnuclease-free water.

Next Generation Sequencing

The concentrations of different PCR products were measured using theDenovix dsDNA fluorescence quantitation kit (Denovix) and multiplexed atequal concentrations with a 20% PhiX spike-in. Sequencing was performedon an Illumina MiSeq with 150 bp paired-end reads using the standardmanufacturer protocol.

Capture of Aptamer 21 from PolyA+ RNA Extract

Isolation of PolyA+ RNA from Cells

Total RNA was extracted from a pellet of 5×10⁶HepG2 cells using theReliaPrep mini-prep kit (Promega) according to the manufacturer'sstandard protocol. The polyA+ RNA fraction was isolated from 50 μLsample of total RNA at 454 ng/μL using the magnetic mRNA isolation kit(New England Biolabs, cat # S1550) according to the manufacturer'sstandard protocol using 450 μL of lysis buffer and 100 μL of beads.

Generating Crosslinked and Click-Biotinylated RNA

A sample of folded aptamer 21 RNA was spiked into a sample of polyA+ RNAextract at a final concentration of 1 nM aptamer 21 and 3 ng/μL polyA+RNA. A 50 μL sample of this RNA mixture was then added to a 0.5 μLaliquot of 100 μM ARK-816 or ARK-2059 in DMSO or a DMSO control and themixture was incubated for 20 min at 37° C. The solution was then dilutedwith 50 μL of 1× folding buffer and then irradiated with long wave UVlight (˜365 nm) for 30 min in a UV crosslinker (Fisher Scientific). Tothis solution was added 1 μL of 5 mM DBCO-biotin (Click Chemistry Tools,cat. # A105) and 1 μL of 0.5 M EDTA pH 8 and then the solution wasincubated at 65° C. for 2 h. The RNA was ethanol precipitated by adding35 μL of water, 2 uL of 5 mg/mL glycogen, 10 μL 3 M NaOAc pH 5, and 250μL ethanol, incubating at −80° C. for 1 h, centrifuging at 20,000g for30 min, washing the pellet twice with 500 μL of 70% ethanol, and thenair drying the pellet.

Fragment RNA

RNA samples were fragmented using the Ambion fragmentation kit (Thermo).RNA pellets were resuspended in 50 μL of 1× fragmentation buffer,incubated at 70° C. for 15 min, and then quenched by the addition of 5μL of stop solution. The sample was then ethanol precipitated by adding50 μL water, 10 μL 3 M NaOAc pH 5, 2 μL 5 mg/mL glycogen and 280 μLethanol, incubating for 1 h at −80° C., centrifuging at 20,000g for 30min, washing the pellet twice with 500 μL of 70% ethanol, and then airdrying the pellet.

Avidin Bead Enrichment and Sequencing Library Preparation

Avidin bead capture, dephosphorylation, first linker ligation, reversetranscription, second adapter ligation, and polymerase chain reactionwere performed as per the “Capture of Aptamer 21 with Click-BiotinylatedProbes” section above.

Size Selection of Sequencing Library

To remove primer dimer and size select the sequencing library, the PCRproduct was run on a 3% agarose gel with 1× SYBR-gold. The region from275 to 400 bp was cut out and the DNA was extracted using the ZymocleanGel DNA Recovery Kit (Zymo Research) according to the manufacturer'ssuggested protocol and eluted into 12 μL of nuclease-free water.

Next Generation Sequencing

Sequencing was performed on a single Illumina HiSeq 4000 lane with 150bp paired-end reads using the standard manufacturer protocol. PEARL-seqInformatics

Genome References

All analyses were referenced to the GRCh38 human genome assembly andGENCODE release 28 transcript annotations, with Aptamer 21 added(AGGGGTAGGCCAGGCAGCCAACTAGCGAGAGCTTAAATCTCTGAGCCCGAGAGGGTTCAGTGCTGCTTATGTGGACGGCTTGAT; SEQ. ID:25).

Read Stitching

To ensure that only high-quality, concordant read pairs were used todefine mutations and reverse transcriptase stalls, reads were firststitched with Paired-End reAd mergeR (PEAR)(https://dx.doi.org/10.1093%2Fbioinformatics % 2Fbtt593), requiring aminimum assembled length of at least 10 nucleotides (nt).

Single-Transcript Read Alignment (SHAPEware)

For all SHAPEware analysis, reads were adapter-trimmed aligned aspreviously described (https://bitbucket. org/arraki stx/shapeware/src)using Trimmomatic (http://dx.doi.org/10.1093/bioinformatics/btu170) andbwa-mem (https://arxiv.org/abs/1303.3997), respectively.

SHAPE Reactivity Calculation (SHAPEware)

Mutations (substitutions, insertions, and deletions) were tabulatedusing bam-readcount (https://github.com/genome/bam-readcount). Mutationswere then filtered to retain only those that can be unambiguously linkedto a given transcript position (ambiguous mutations could arise frommultiple positions). SHAPE reactivities were defined based upon theexcess of mutations in SHAPE reagent-treated sample compared tountreated sample, normalized to an unfolded control:

${Reactivity} = {\frac{{Mut}_{treated} - {Mut}_{untreated}}{{Mut}_{denatured}}.}$

Reactivities were then further normalized within each transcript asdescribed in Deigan et al. (PNAS Jan. 6, 2009, 106 (1) 97-102).

Transcriptome-Wide Read Alignment (PEARL-seq)

Stitched reads were then processed with Cutadapt(http://dx.doi.org/10.14806/ej.17.1.200) with at least 5-nts of overlapand a maximum of 20% mismatches to simultaneously 1) define a unique6-nt unique molecular identifier (UMI) in the correct adapter context(ATATAGGN6AGATCGG) (SEQ. ID:35) and 2) trim away adapters to allow moreprecise definition of fragment termini. UMIs were appended to readnames, and reads were mapped the against the genome and transcriptomereferences (plus Aptamer 21) using the STAR aligner(http://dx.doi.org/10.1093/bioinformatics/bts635) with at most 10%mismatches. Groups of reads with identical or near-identical UMIs werethen collapsed using the Directional Adj acency methods of UMI-tools(http://dx.doi.org/10.1101/gr.209601.116) with default parameters. As aresult, PCR duplicates were removed from the data to avoid potentialartifacts that might introduce bias or variance.

Definition of RT Stall Sites

Sites of interaction between probe and transcripts were defined byreverse transcriptase (RT) stalling sites. RT stalling sites weredefined based upon the mapped position of the 5′ end of a trimmed read.For short defined transcripts such as Aptamer 21, high-confidence RTstall sites were defined from reads with 3′ ends mapping to the precisetranscript end. The frequency of high-confidence stall sites are plottedfor each position in Aptamer 21.

Peakcalling (PEARL-seq)

True sites of small molecule-transcript interaction were defined basedupon significant enrichment of stall sites in a PEARL-seq probe comparedto a warhead-only control. These peaks are expected to be quite narrowbased upon the single-nucleotide resolution of RT stall sites. Thus, wedeveloped a peakcalling method optimized to detect these narrow peaksand thus identify sites enriched for RT sites in probe when compared toa warhead-only control. Briefly, uniquely mapping reads were trimmed toretain their 5′ most nucleotide only. These 5′ ends were then countedacross 10-nt bins throughout the whole genome using Deeptools(http://dx.doi.org/10.1093/nar/gkw257) combined with custom scripts.Each bin with detectable read 5′ ends was tested for significantenrichment with the Empirical Analysis of Digital Gene Expression Datain R (edgeR) pipeline (https://doi.org/doi:10.18129/B9.bioc.edgeR),using Benjamini-Hochberg multiple hypothesis correction. Peaks with bothpositive enrichment in probe over control and an FDR <0.01 wereconsidered to contain probe-induced RT stalling events corresponding toprobe-transcript interactions.

Example 7 Surface Plasmon Resonance Assay for Aptamer 21

Surface plasmon resonance (SPR) may be used to screen ligands and hookand click constructs for binding to a target RNA of interest. SPR isespecially useful for monitoring biomolecular interactions in real time.Typically, target species and unrelated control are immobilized to asensor chip, then analytes (compounds/fragments) are flowed over thesurface. Binding of the compound to target species results in increaseof SPR signal (association phase). Washing away bound compound withbuffer results in a decrease of SPR signal (dissociation phase). Fittingof sensorgrams recorded at different compound concentrations isperformed to an appropriate interaction model. The method allowsextraction of kinetic parameters (k_(a), k_(d)→K_(D)).Requirements/limitations include that the k_(a)/k_(d) values be inreasonable ranges; and the target size must not be too large (<100 kDa).It is an excellent method to screen fragments and profile or validatehits. BC4000 may be used for primary screening (up to 4,000 datapts/week). Biacore T200 is suitable for hit profiling and validation.

Aptamer evolution for codeine binding has been achieved and theaptamer's binding constant determined by use of SPR. Win, N. M. et al.,Nucleic Acids Research 2006, 34(19), 5670-5682. See, e.g., Chang, A. L.et al., Anal. Chem. 2014, 86, 3273-3278.

In the PEARL-seq context, SPR allows monitoring binding of “hooks” toDNA/RNA aptamers. The target species is immobilized to sensor chip,analytes (i.e. hooks) are flowed over surface (association phase),DNA/RNA aptamer is flowed over surface (plateau phase), competitorcompound is washed over surface (dissociation phase), thus yieldingbinding data.

Sensor Chip Surface Preparation

Experiments were performed on a MASS-2 (Sierra Sensors) at 25° C. A highcapacity amine chip was equilibrated with PBS. The chip was conditionedwith alternating injections of 10 mM HCl and 10 mM NaOH in 1 M NaCl. Thecarboxymethylated dextran of the surface of the amine chip was activatedfor 7 minutes at a flow rate of 10 μL/min using a 1:1 volume ratio of0.4 M 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (Sierra) and 0.1 MN-hydroxysuccinimide (Sierra). Neutravidin (70 μg/mL, Thermofisher) wasinjected over the activated surface for 10 minutes at a flow rate of 10μl/min. Excess activated groups were blocked by an injection of 1 Methanolamine, pH 8.5 (Sierra) for 7 minutes at a flow rate of 10 μl/min.A final injection of 10 mM NaOH in 1 M NaCl for 7 minutes at 10 μl/minwas used to remove any unbound material to the chip. The immobilizationreaction typically yielded approximately 12,000 resonance units (RU) ofneutravidin. At least one spot in a channel was not injected with RNAand was used as a background control. Unrelated RNA was also used as abackground control.

RNA Preparation

A 1 μM sample of biotin-aptamer 21 was prepared in RNAse free water,heated to 95 ° C. for 3 minutes, cooled on ice for 4 minutes, dilutedwith an equal volume 2× folding buffer (40 mM Tris-HCl, pH 8.0, 6 mMMgCl₂, 200 mM KCl), and incubated at 37° C. for 30 minutes. The finalconcentration of RNA was 0.5 μM.

RNA Surface Capture

The MASS-2 was primed 2 times with 20 mM Tris-HCl, pH 8.0, 3 mM MgCl₂,100 mM KCl (Capture Buffer). RNA was injected over the neutravidinsurface for 7 minutes at a flow rate of 10 μl/min. Capture levelstypically reached approximately 3500-4500 of resonance units of aptamer21.

Compound Testing

Compounds were diluted2-fold in 100% DMSO at a starting concentration of500 μM. Dilutions of 1:100, compound to buffer resulted in compoundsolutions in 20 mM Tris-HCl, pH 8.0, 3 mM MgCl₂, 100 mM KCl, 1% DMSO.

The MASS-2 was primed 2 times with 20 mM Tris-HCl, pH 8.0, 3 mM MgCl₂,100 mM KCl, 1% DMSO (running buffer). Prior to testing compounds 3injections of running buffer were used to equilibrate the sensorsurface. Injections of DMSO correction solutions ranging from 0.6%-1.8%DMSO were injected over the surface for 30 μl at a flow rate of 30μl/min to generate a DMSO correction curve for data analysis. Compound(120 μL) was injected over the RNA surface at a flow rate of 10 μl/minwith a dissociation time of 240 sec.

Data Analysis

Data processing and analysis were done using Sierra Analyzer Software(Sierra Sensors). A double-referencing method was performed to processall datasets and a DMSO correction curve was applied to account for anydifferences in bulk refractive index changes between samples and runningbuffer. Double-referenced data were fit to a 1:1 binding model forkinetic analysis. The calculated K_(D) was ˜0.8 nM under theseconditions.

Example 8 Preparation of PreQi RNA Photoprobe

Use of the PreQi riboswitch and preparation of small molecule ligandsfor it are described in Roth, A. et al., Nature Structural & MolecularBiology 2007, 14(4), 308-317, which is hereby incorporated by reference.

Compound 24: To a suspension of 23 (500 mg, 1.19 mmol, 1 eq,) andtert-butyl (2-(2-(2-aminoethoxy)ethoxy)ethyl)carb am ate (354 mg, 1.43mmol, 1.2 eq.) in methanol (14.0 mL) was added sodium sulfate (14 mg,0.09 mmol, 0.08 eq.) at room temperature. The resulting suspension wasstirred at room temperature for 2 h. Sodium borohydride (135 mg, 3.57mmol, 3.0 eq.) was then added in small portions to the reaction mixture,then stirring at room temperature was maintained for and additional 4 h.The reaction mixture was diluted with ethyl acetate (250 mL), then waswashed with sequential 50 mL portions of water (thee times) and sat. aq.NaCl solution. The product solution was dried over Na₂SO₄, filtered, andthe filtrate concentrated under reduced pressure. The obtained crudematerial was purified by reverse phase chromatography using C₁₈-silicagel (42-45% CH₃CN in 10 mM NH₄HCO₃ in water) to afford 24 as anoff-white solid (302 mg, 39% yield). ¹H NMR (400 MHz, DMSO-d₆, δ): 10.61(s, 1 H), 10.32 (br s,1 H), 7.38 (s, 1 H), 7.31-7.28 (m, 12 H),7.24-7.19 (m, 3 H), 6.82 (t, J=5.6 Hz, 1 H), 6.31 (d, J=2 Hz, 1 H), 3.56(s, 2 H), 3.46-3.35 (m, 11 H), 3.08-3.03 (m, 2 H), 1.36 (s, 9 H). MS(ESI-MS): m/z calc. for C₃₇H₄₄N₆O₅[MH]⁺ 653.34; found 653.14.

Compound 25 (1-23): A stirring solution of 24 (21 mg, 32 μmol, 1 eq.) inCH₃OH (1.0 mL) at room temperature was treated dropwise with a 1.25 MCH₃OH solution of HCl 583 μL, 0.73 mmol, 23 eq.). The resulting mixturewas allowed to stir at room temperature for 24 h, then the precipitatedsolids were collected by filtration. The resulting crude solid wastriturated with sequential 10 mL portions of pentane (twice) and diethylether (twice) to afford the intermediate primary amine as a white solid.The primary amine (10 mg, 32 μmol, 1 eq.) was resuspended in DMF (1.0mL), then was treated with N,N-diisopropylethylamine (22 μL, 0.13 mmol,4.0 eq.), and 2,5-dioxopyrrolidin-1-yl3-(3-methyl-3H-diazirin-3-yl)propanoate (7.6 mg, 34 μmol, 1.05 eq.). Theresulting mixture was maintained at room temperature for 16 h, then wasimmediately loaded onto a C₁₈-silica gel column, eluting with 0-70%CH₃CN in water containing 0.1% formic acid). Fractions containing thedesired product were combined and partially evaporated under reducedpressure to remove CH₃CN, then were frozen and lyophilized to afford thedesired product 1-23 as a white solid (formate salt, 9 mg, 60% yield).

Example 9 Synthesis of Additional Exemplary Photoprobe Compounds

Compound 26: To a solution of 3-amino-4-methylbenzoic acid (4.00 g, 26.5mmol, 1 eq.) in acetic acid (80 mL) was added2,6-difluoro-3-hydroxybenzaldehyde (5.01 g, 31.7 mmol, 1.2 eq.) at 0° C.The reaction was slowly warmed to room temperature and stirred at roomtemperature for 3 h. The reaction mixture was again cooled to 0° C.NaCNBH₃ (3.32 g, 52.9 mmol, 2.0 eq.) was added, in small portions. Thereaction mixture was allowed to warm to room temperature, then wasstirred at room temperature for 16 h. The resulting reaction mixture waspoured into ice-cold water (500 mL). The resulting precipitate wascollected by filtration and washed with water (3×25 mL). The obtainedsolid was dried under high vacuum to afford 26 as a white solid (6.00 g,62% yield). ¹H NMR (400 MHz, DMSO-d₆) δ 12.48 (br s, 1H), 9.74 (s, 1 H),7.22 (d, J=1.2 Hz, 1 H), 7.13 (dd, J=7.6, 1.6 Hz, 1 H), 7.05 (d, J=8.0Hz, 1 H), 6.86-6.83 (m, 2H), 5.38 (t, J=5.6 Hz, 1 H), 4.36 (d, J=5.2 Hz,2 H), 2.11 (s, 3H). MS (ESI-MS): m/z calcd for C₁₅H₁₃F₂NO₃ ⁺=294.09,found 294.16.

Compound 27: Compound 27 was synthesized according to General ProcedureA from (2.00 g, 6.82 mmol) and methyl(S)-1,2,3,4-tetrahydroisoquinoline-3-carboxylate hydrochloride in DMF(20 mL) at room temperature. Following stirring at room temperature for3 h, the reaction mixture was diluted with water and the resultingsolids collected by filtration. The crude product was purified by flashcolumn chromatography over silica gel (40% EtOAc/hexanes) to afford 27as a light pink solid (1.60 g, 34% yield). MS (ESI-MS): m/z calcd forC₂₆H₂₄F₂N₂O₄ ⁺=467.17, found 467.22.

Compound 28: To a stirred solution of 27 (1.60 g, 3.93 mmol, 1 eq.) inTHF:MeOH:Water (4:2:1, 11.2 mL) was added LiOH.H₂O (0.43 g, 10.3 mmol,3.0 eq.) at room temperature.

The reaction mixture was stirred at room temperature for 3 h, then wasevaporated under vacuum. The obtained crude material was diluted withwater and washed with diethyl ether. The aqueous layer was separated,acidified using 1N HCl and extracted with ethyl acetate (4×100 mL). Thecombined organic layer was washed with brine solution (150 mL), driedover Na₂SO₄, filtered and concentrated under reduced pressure. Theobtained crude material was purified by column chromatography oversilica gel (7% MeOH/DCM) to afford 28 as an off-white solid (1.55 g,100% yield). ¹H NMR (400 MHz, DMSO-d₆) δ 12.79 (br s, 1 H), 9.76 (s, 1H), 7.26-7.13 (m, 3 H), 7.07-7.03 (m, 1 H), 6.96-6.78 (m, 3 H), 6.63 (d,J=8.8 Hz, 1 H), 6.58-6.52 (m, 1 H), 5.39-5.38 (m, 1 H), 5.13-4.42 (m, 3H), 4.32-4.30 (m, 2 H), 3.18-3.11 (m, 2 H), 2.10 (d, J=8.4 Hz, 3 H). MS(ESI-MS): m/z calcd for C₂₅H₂₂F₂N₂O₄ ⁺=453.16 found 453.27.

Compound 29: Compound 29 (ARK-852) was synthesized according to GeneralProcedure A from 26 (100 mg, 351 μmol) and(S)-1,2,3,4-tetrahydroisoquinoline-3-carboxamide in DMF (2 mL) at roomtemperature. The resulting dark mixture was allowed to stir at roomtemperature for 60 minutes, then was purified by reverse-phase flashcolumn chromatography over C₁₈ silica gel (C₁₈-silica gel, eluting with0-100% acetonitrile in water containing 0.1% formic acid) to afford 29as an off-white solid (formate salt, 21 mg, 12% yield). MS (ESI-MS):t_(R)=1.54 min; m/z calcd for C₃₀H₂₇F₂N₃O₃ ⁺=498.1, found 520.1([M+Na]⁺).

Compound 30: Compound 30 was prepared by General Procedure A from 26(3.00 g, 10.2 mmol) and (S)-4-phenylphenylalanine methyl esterhydrochloride. After stirring at room temperature for 4 h, the reactionmixture was poured into ice-cold water (250 mL). The resulting solidswere collected by filtration and purified by column chromatography oversilica gel (30% EtOAc/hexanes) to afford 30 as a white solid (4.20 g,77% yield). MS (ESI-MS): m/z calcd for C₃₁H₂₈F₂N₂O₄ ⁺=531.04, found531.27.

Compound 31: Compound 31 was prepared analogously to 28 above from 30(4.20 g, 7.91 mmol). The crude product was purified by columnchromatography over silica gel (7% MeOH in CH₂Cl₂) to afford 31 as awhite solid (1.70 g, 42% yield). ¹H NMR (400 MHz, DMSO-d₆) δ 12.77 (brs, 1 H), 9.76 (s, 1 H), 8.42 (s, 1 H), 7.60-7.54 (m, 4 H), 7.40- 7.33(m, 5 H), 7.08-7.01 (m, 3 H), 6.86-6.84 (m, 2 H), 5.21-5.19 (m, 1 H),4.56 (s, 1 H), 4.33 (s, 2 H), 3.18-3.10 (m, 2 H), 2.07 (s, 3 H). MS(ESI-MS): m/z calcd for C₃₀H₂₆F₂N₂O₄ ⁺517.19, found 517.07.

Compound 32: Compound 32 (ARK-850) was synthesized according to GeneralProcedure A from 26 (100 mg, 351 μmol) and (S)-4-phenylphenylalaninamidein DIVIF (2 mL) at room temperature. The resulting dark mixture wasallowed to stir at room temperature for 30 minutes, then was partitionedbetween sat. aq. NaHCO₃ solution (30 mL) and ethyl acetate (30 mL). Theaqueous phase was extracted with 30 mL EtOAc, then the combined extractswere washed with 30 mL water and 30 mL sat. aq. NaCl solution. Theproduct solution was dried over MgSO₄, filtered, and concentrated toafford the crude product as a brown oil. The crude product was purifiedby reverse-phase flash column chromatography over C₁₈ silica gel (0-100%CH₃CN in water containing 0.1% formic acid). Fractions containing 32were combined and partially evaporated to remove CH₃CN, then theresulting suspension was partitioned between sat. aq. NaHCO₃ solution(30 mL) and EtOAc (30 mL). The aqueous phase was extracted with 30 mLEtOAc, then the combined extracts were washed with 30 mL water and 30 mLsat. aq. NaCl solution. The product solution was dried over MgSO₄,filtered, and concentrated to afford 32 as an off-white foam (62 mg, 40%yield). MS (ESI-MS): t_(R)=1.67 min; m/z calcd for C₃₀H₂₇F₂N₃O₃ ⁺=516.1,found 499.1 ([M+H+NH₃]⁺.

Compound 33: Compound 33 was synthesized according to General ProcedureA from 28 (30 mg, 66 μmol) and NH₂-PEG₁-CO₂ ^(t)Bu. The reaction mixturewas stirred at room temperature for 1 h, then was purified by columnchromatography (C₁₈ silica gel, eluting with 0-100% CH₃CN in watercontaining 0.1% formic acid) to afford 33 as a colorless film (40 mg,98% yield). MS (ESI-MS): m/z calcd for C₃₄H₄₀F₂N₃O₆ ⁺=624.3, found624.3.

Compound 34: Compound 34 was synthesized according to General ProcedureA from 28 (30 mg, 66 μmol) and NH₂-PEG₂-CO₂ ^(t)Bu. The reaction mixturewas stirred at room temperature for 1 h, then was purified by columnchromatography (C₁₈ silica gel, eluting with 0-100% CH₃CN in watercontaining 0.1% formic acid) to afford 34 as a colorless film (41 mg,93% yield). MS (ESI-MS): m/z calcd for C₃₆H₄₄F₂N₃O₇ ⁺=668.3, found668.3.

Compound 35: Compound 35 was synthesized according to General ProcedureA from 28 (30 mg, 66 μmol) and NH₂-PEG₄-CO₂ ^(t)Bu. The reaction mixturewas stirred at room temperature for 1 h, then was purified by columnchromatography (C₁₈ silica gel, eluting with 0-100% CH₃CN in watercontaining 0.1% formic acid) to afford 35 as a colorless film (47 mg,94% yield). MS (ESI-MS): m/z calcd for C₄₀H₅₂F₂N₃O₉ ⁺=756.4, found756.4.

Compound 36: Compound 36 was synthesized according to General ProcedureA from 28 (30 mg, 66 μmol) and NH₂-PEG₂-NHB_(OC). The reaction mixturewas stirred at room temperature for 1 h, then was purified by columnchromatography (C₁₈ silica gel, eluting with 0-100% CH₃CN in watercontaining 0.1% formic acid) to afford 36 as a colorless film (35 mg,82% yield). MS (ESI-MS): m/z calcd for C₃₄H₄₁F₂N₄O₆ ⁺=639.3, found639.3.

Compound 37: Compound 37 was synthesized according to General ProcedureA from 28 (100 mg, 221 μmol) and NH₂-PEG₂-NHB_(OC). The reaction mixturewas stirred at room temperature for 1 h, then was purified by columnchromatography (C₁₈ silica gel, eluting with 0-100% CH₃CN in watercontaining 0.1% formic acid) to afford 37 as a colorless film (126 mg,84% yield). MS (ESI-MS): m/z calcd for C₃₆H₄₅F₂N₄O₇ ⁺=683.3, found683.3.

Compound 38: Compound 33 was synthesized according to General ProcedureA from 28 (30 mg, 66 μmol) and NH₂-PEG₄-NHB_(OC). The reaction mixturewas stirred at room temperature for 1 h, then was purified by columnchromatography (C₁₈ silica gel, eluting with 0-100% CH₃CN in watercontaining 0.1% formic acid) to afford 38 as a colorless film (37 mg,72% yield). MS (ESI-MS): m/z calcd for C₄₀H₅₃F₂N₄O₉ ⁺=771.4, found771.4.

General Procedure C—Synthesis of Photoprobes from Boc- or tert-butylester-Protected Ligands: The Boc- or tent-butyl ester-protected ligand(1 eq.) was treated with neat trifluoroacetic acid (2 mL). The mixturewas allowed to stir at room temperature for 5 minutes, then wasconcentrated to dryness under reduced pressure. The residue was thenresuspended in DMF (2 mL), then was treated with DIEA (10 eq.), HATU(2.0 eq.) and the photoreactive warhead (as an free amine, aminehydrochloride, or carboxylic acid). The resulting mixtures were stirredat room temperature until LC-MS analysis indicated that the reaction wascomplete, then the photoprobes were purified by reverse-phase flashcolumn chromatography. Fractions containing the desired products werecombined and concentrated to remove CH₃CN, then were frozen andlyophilized to afford the final photoprobes as white solids.

Compound 39: Compound 39 (I-24) was synthesized according to GeneralProcedure C from 33 (33 mg, 53 μmol)and2-(3-(2-azidoethyl)-3H-diazirin-3-yl)ethan-1-amine. See Pan, S.;Jang, S.; Wang, D.; Liew, S.; Li, Z.; Lee, J.; Yao, S. Q. Angew. Chem.Int. Ed., 2017, 39, 11816-11821. After stirring at room temperature for1 h, the mixture was purified by flash column chromatography over C₁₈silica gel to afford 39 as a white solid (17 mg, 46% yield). MS(ESI-MS): m/z calcd for C₃₅H₄₀F₂N₉O₅ ⁺=704.3, found 704.3.

Compound 40: Compound 40 (I-25) was synthesized according to GeneralProcedure C from 34 (22 mg, 33 μmol)and2-(3-(2-azidoethyl)-3H-diazirin-3-yl)ethan-1-amine. After stirring atroom temperature for 1 h, the mixture was purified by flash columnchromatography over C₁₈ silica gel to afford 40 as a white solid (15 mg,62% yield). MS (ESI-MS): m/z calcd for C₃₇H₄₄F₂N₉O₆ ⁺=748.3, found748.3.

Compound 41: Compound 41 (I-26) was synthesized according to GeneralProcedure C from 35 (32 mg, 43 μmol)and2-(3-(2-azidoethyl)-3H-diazirin-3-yl)ethan-1-amine. After stirring atroom temperature for 1 h, the mixture was purified by flash columnchromatography over C₁₈ silica gel to afford 41 as a white solid (16 mg,45% yield). MS (ESI-MS): m/z calcd for C₄₁H₅₂F₂N₉O₈ ⁺=836.4, found836.4.

Compound 42: Compound 42 (I-27) was synthesized according to GeneralProcedure C from 33 (33 mg, 53 μmol) and 4-azidoaniline hydrochloride.After stirring at room temperature for 1 h, the mixture was purified byflash column chromatography over C₁₈ silica gel to afford 42 as a whitesolid (14 mg, 39% yield). MS (ESI-MS): m/z calcd for C₃₆H₃₆F₂N₇O₅⁺=684.3, found 684.3.

Compound 43: Compound 43 (I-28) was synthesized according to GeneralProcedure C from 34 (22 mg, 33 μmol) and 4-azidoaniline hydrochloride.After stirring at room temperature for 1 h, the mixture was purified byflash column chromatography over C₁₈ silica gel to afford 43 as a whitesolid (11 mg, 43% yield). MS (ESI-MS): m/z calcd for C₃₈H₄₀F₂N₇O₆⁺=728.4, found 728.4.

Compound 44: Compound 44 (I-29) was synthesized according to GeneralProcedure C from 35 (32 mg, 43 μmol) and 4-azidoaniline hydrochloride.After stirring at room temperature for 1 h, the mixture was purified byflash column chromatography over C₁₈ silica gel to afford 44 as a whitesolid (17 mg, 49% yield). MS (ESI-MS): m/z calcd for C₄₂H₄₈F₂N₇O₈⁺=816.4, found 816.4.

Compound 45: Compound 45 (I-30) was synthesized according to GeneralProcedure C from 36 (11 mg, 17 μmol) and 4-azidobenzoic acid. Afterstirring at room temperature for 1 h, the mixture was purified by flashcolumn chromatography over C₁₈ silica gel to afford 45 as a white solid(10 mg, 85% yield). MS (ESI-MS): m/z calcd for C₃₆H₃₆F₂N₇O₅ ⁺=684.3,found 684.3.

Compound 46: Compound 46 (I-31) was synthesized according to GeneralProcedure C from 37 (14 mg, 21 μmol) and 4-azidobenzoic acid. Afterstirring at room temperature for 1 h, the mixture was purified by flashcolumn chromatography over C₁₈ silica gel to afford 46 as a white solid(11 mg, 71% yield). MS (ESI-MS): m/z calcd for C₃₈H₄₀F₂N₇O₆ ⁺=728.4,found 728.4.

Compound 47: Compound 47 (I-32) was synthesized according to GeneralProcedure C from 38 (21 mg, 27 μmol) and 4-azidobenzoic acid. Afterstirring at room temperature for 1 h, the mixture was purified by flashcolumn chromatography over C₁₈ silica gel to afford 47 as a white solid(12 mg, 54% yield). MS (ESI-MS): m/z calcd for C₄₂H₄₈F₂N₇O₈ ⁺=816.4,found 816.4.

Compound 48: Compound 48 (1-33) was synthesized according to GeneralProcedure C from 37 (126 mg, 184 μmol) and3-azido—S—(azidomethyl)benzoic acid. After stirring at room temperaturefor 16 h, the mixture was purified by flash column chromatography overC₁₈ silica gel to afford 48 as a white solid (26 mg, 18% yield). MS(ESI-MS): m/z calcd for C₃₉H₄₁F₂N₁₀O₆ ⁺=783.4, found 783.4.

Compound 49: Compound 49 was synthesized according to General ProcedureA from 31 (30 mg, 58 μmol) and NH₂-PEG₁-NHB_(OC). The reaction mixturewas stirred at room temperature for 1 h, then was purified by columnchromatography (C₁₈ silica gel, eluting with 0-100% CH₃CN in watercontaining 0.1% formic acid) to afford 49 as a colorless film (27 mg,65% yield). MS (ESI-MS): m/z calcd for C₃₉H₄₅F₂N₄O₆ ⁺=703.3, found703.3.

Compound 50: Compound 50 was synthesized according to General ProcedureA from 31 (30 mg, 58 μmol) and NH₂-PEG₂-NHB_(OC). The reaction mixturewas stirred at room temperature for 1 h, then was purified by columnchromatography (C₁₈ silica gel, eluting with 0-100% CH₃CN in watercontaining 0.1% formic acid) to afford 50 as a colorless film (31 mg,69% yield). MS (ESI-MS): m/z calcd for C₄₁H₄₉F₂N₄O₇ ⁺=747.3, found747.3.

Compound 51: Compound 51 was synthesized according to General ProcedureA from 31 (30 mg, 58 μmol) and NH₂-PEG₄-NHB_(OC). The reaction mixturewas stirred at room temperature for 1 h, then was purified by columnchromatography (C₁₈ silica gel, eluting with 0-100% CH₃CN in watercontaining 0.1% formic acid) to afford 51 as a colorless film (41 mg,84% yield). MS (ESI-MS): m/z calcd for C₄₅H₅₇F₂N₄O₉ ⁺=835.3, found835.3.

Compound 52: Compound 52 (I-34) was synthesized according to GeneralProcedure C from 49 (25 mg, 36 μmol) and 4-azidobenzoic acid. Afterstirring at room temperature for 1 h, the mixture was purified by flashcolumn chromatography over C₁₈ silica gel to afford 52 as a white solid(9 mg, 34% yield). MS (ESI-MS): m/z calcd for C₄₁H₄₀F₂N₇O₅ ⁺=748.3,found 748.3.

Compound 53: Compound 53 (I-35) was synthesized according to GeneralProcedure C from 50 (30 mg, 40 μmol) and 4-azidobenzoic acid. Afterstirring at room temperature for 1 h, the mixture was purified by flashcolumn chromatography over C₁₈ silica gel to afford 53 as a white solid(6 mg, 19% yield). MS (ESI-MS): m/z calcd for C₄₃H₄₄F₂N₇O₆ ⁺=792.3,found 792.3.

Compound 54: Compound 54 (I-36) was synthesized according to GeneralProcedure C from 51 (31 mg, 37 μmol) and 4-azidobenzoic acid. Afterstirring at room temperature for 1 h, the mixture was purified by flashcolumn chromatography over C₁₈ silica gel to afford 54 as a white solid(23 mg, 71% yield). MS (ESI-MS): m/z calcd for C₄₇H₅₂F₂N₇O₈ ⁺=880.4,found 880.4.

While we have described a number of embodiments of this invention, it isapparent that our basic examples may be altered to provide otherembodiments that utilize the compounds and methods of this invention.Therefore, it will be appreciated that the scope of this invention is tobe defined by the appended claims rather than by the specificembodiments that have been represented by way of example.

We claim:
 1. A compound of Formula I, II, III, II-a, II-b, or II-c:

or a pharmaceutically acceptable salt thereof; wherein: Ligand is asmall molecule RNA binder; T¹ is a bivalent tethering group (in FormulasI, II, II-a, or II-c) or a trivalent tethering group (in Formula III);or T¹ may be a covalent bond (in Formula II-a); T² is a covalent bond ora bivalent tethering group; R^(CG) is a click-ready group or a pull-downgroup; and R^(mod) is a photoactivatable group. 2-5. (canceled)
 6. Thecompound of claim 1, wherein Ligand is selected from aheteroaryldihydropyrimidine (HAP), a macrolide, an alkaloid, anaminoglycoside, a tetracycline, a SMN2 ligand, a pleuromutilin,theophylline or an analogue thereof, ribocil or an analogue thereof, asubstituted anthracene, a substituted triptycene, an oxazolidinone, orCPNQ or an analogue thereof; wherein Ligand may be optionallysubstituted with one or more substituents.
 7. The compound of claim 1,wherein Ligand is selected from an optionally substitutedheteroaryldihydropyrimidine (HAP), erythromycin, azithromycin,berberine, palmatine, a paromomycin, a neomycin, a kanamycin,doxycycline, oxytetracycline, pleuromutilin, theophylline or an analoguethereof, ribocil or an analogue thereof, LMI070 (NVS-SM1), a substitutedtriptycene, linezolid, tedizolid, or CPNQ or an analogue thereof;wherein Ligand may be optionally substituted with 1, 2, 3, or 4substituents.
 8. The compound of claim 1, wherein T¹ is selected from aC₁₋₂₀ bivalent straight or branched hydrocarbon chain wherein 1, 2, 3,4, 5, 6, 7, 8, 9, or 10 methylene units of the chain are independentlyand optionally replaced with a natural or non-natural amino acid, —O—,—C(O)—, —C(O)O—, —OC(O)—, —N(R)—, —C(O)N(R)—, —(R)NC(O)—, —OC(O)N(R)—,—(R)NC(O)O—, —N(R)C(O)N(R)—, —S—, —SO—, —SO₂—, —SO₂N(R)—, —(R)NSO₂—,—C(S)—, —C(S)O—, —OC(S)—, —C(S)N(R)—, —(R)NC(S)—, —(R)NC(S)N(R)—, or-Cy-; and 1-20 of the methylene units of the chain are independently andoptionally replaced with —OCH₂CH₂—; wherein each -Cy- is independently abivalent optionally substituted 3-8 membered saturated or partiallyunsaturated monocyclic carbocyclic ring, optionally substitutedphenylene, an optionally substituted 4-8 membered saturated or partiallyunsaturated monocyclic heterocyclic ring having 1-3 heteroatomsindependently selected from nitrogen, oxygen, or sulfur, an optionallysubstituted 5-6 membered monocyclic heteroaromatic ring having 1-4heteroatoms independently selected from nitrogen, oxygen, or sulfur, anoptionally substituted 8-10 membered bicyclic or bridged bicyclicsaturated or partially unsaturated heterocyclic ring having 1-5heteroatoms independently selected from nitrogen, oxygen, or sulfur, oran optionally substituted 8-10 membered bicyclic or bridged bicyclicheteroaromatic ring having 1-5 heteroatoms independently selected fromnitrogen, oxygen, or sulfur; and each R is independently hydrogen or anoptionally substituted group selected from C₁₋₆ aliphatic, a 3-8membered saturated or partially unsaturated monocyclic carbocyclic ring,phenyl, an 8-10 membered bicyclic aromatic carbocyclic ring, a 4-8membered saturated or partially unsaturated monocyclic heterocyclic ringhaving 1-2 heteroatoms independently selected from nitrogen, oxygen, orsulfur, a 5-6 membered monocyclic heteroaromatic ring having 1-4heteroatoms independently selected from nitrogen, oxygen, or sulfur, oran 8-10 membered bicyclic heteroaromatic ring having 1-5 heteroatomsindependently selected from nitrogen, oxygen, or sulfur.
 9. (canceled)10. The compound of claim 2, wherein T² is selected from a C₁₋₂₀bivalent straight or branched hydrocarbon chain wherein 1, 2, 3, 4, 5,6, 7, 8, 9, or 10 methylene units of the chain are independently andoptionally replaced with a natural or non-natural amino acid, —O—,—C(O)—, —C(O)O—, —OC(O)—, —N(R)—, —C(O)N(R)—, —(R)NC(O)—, —OC(O)N(R)—,—(R)NC(O)O—, —N(R)C(O)N(R)—, —S—, —SO—, —SO₂—, —SO₂N(R)—, —(R)NSO₂—,—C(S)—, —C(S)O—, —OC(S)—, —C(S)N(R)—, —(R)NC(S)—, —(R)NC(S)N(R)—, or-Cy-; and 1-20 of the methylene units of the chain are independently andoptionally replaced with —OCH₂CH₂—; wherein each -Cy- is independently abivalent optionally substituted 3-8 membered saturated or partiallyunsaturated monocyclic carbocyclic ring, optionally substitutedphenylene, an optionally substituted 4-8 membered saturated or partiallyunsaturated monocyclic heterocyclic ring having 1-3 heteroatomsindependently selected from nitrogen, oxygen, or sulfur, an optionallysubstituted 5-6 membered monocyclic heteroaromatic ring having 1-4heteroatoms independently selected from nitrogen, oxygen, or sulfur, anoptionally substituted 8-10 membered bicyclic or bridged bicyclicsaturated or partially unsaturated heterocyclic ring having 1-5heteroatoms independently selected from nitrogen, oxygen, or sulfur, oran optionally substituted 8-10 membered bicyclic or bridged bicyclicheteroaromatic ring having 1-5 heteroatoms independently selected fromnitrogen, oxygen, or sulfur; and each R is independently hydrogen or anoptionally substituted group selected from C₁₋₆ aliphatic, a 3-8membered saturated or partially unsaturated monocyclic carbocyclic ring,phenyl, an 8-10 membered bicyclic aromatic carbocyclic ring, a 4-8membered saturated or partially unsaturated monocyclic heterocyclic ringhaving 1-2 heteroatoms independently selected from nitrogen, oxygen, orsulfur, a 5-6 membered monocyclic heteroaromatic ring having 1-4heteroatoms independently selected from nitrogen, oxygen, or sulfur, oran 8-10 membered bicyclic heteroaromatic ring having 1-5 heteroatomsindependently selected from nitrogen, oxygen, or sulfur.
 11. Thecompound of claim 1, wherein R^(mod) is selected from a functional groupthat generates a radical, an aryl or heteroaryl carbocation, a nitrene,or a carbene intermediate upon irradiation with ultraviolet (UV)radiation; and wherein R^(mod) is capable of reacting with a target RNAto which Ligand binds to produce a covalent bond with the target RNAupon irradiation.
 12. (canceled)
 13. The compound of claim 1, whereinR^(mod) is selected from

wherein Y⁻ is a pharmaceutically acceptable anion.
 14. A compound ofFormula X-a:

or a tautomer or pharmaceutically acceptable salt thereof, wherein: Ar¹is an optionally substituted phenyl or optionally substituted 5-6membered monocyclic heteroaromatic ring having 1-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; Ar² is anoptionally substituted 5-6 membered monocyclic heteroaromatic ringhaving 1-4 heteroatoms independently selected from nitrogen, oxygen, orsulfur, or an optionally substituted 8-10 membered bicyclicheteroaromatic ring having 1-5 heteroatoms independently selected fromnitrogen, oxygen, or sulfur; X is selected from a bivalent C₁₋₃ alkylenechain wherein 1-2 methylene units of the chain are independently andoptionally replaced with —O—, —NR⁶—, —S—, —C(O)—, —CO₂——CS—, —C(NR⁶)—,—S(O)—, or —S(O)₂—; R¹ is selected from —C(O)R⁶, —CO₂R, —C(O)NR₂, —C₁₋₆aliphatic, —CN, —(CH₂)₁₋₃OR, —(CH₂)₁₋₃NHR, —N(R)C(O)OR⁶, —N(R⁶)C(O)R,—OC(O)R, —OR, —NHR⁶, or —N(R)C(O)NHR; R² is a photoactivatable groupthat optionally comprises a click-ready group if R³ is absent; R³ isabsent or is a click-ready group or a pull-down group; each R⁶ isindependently hydrogen or C₁₋₆ alkyl optionally substituted with 1, 2,3, 4, 5, or 6 deuterium or halogen atoms; each R is independentlyhydrogen or an optionally substituted group selected from C₁₋₆aliphatic, a 3-8 membered saturated or partially unsaturated monocycliccarbocyclic ring, phenyl, an 8-10 membered bicyclic aromatic carbocyclicring, a 4-8 membered saturated or partially unsaturated monocyclicheterocyclic ring having 1-2 heteroatoms independently selected fromnitrogen, oxygen, or sulfur, a 5-6 membered monocyclic heteroaromaticring having 1-4 heteroatoms independently selected from nitrogen,oxygen, or sulfur, or an 8-10 membered bicyclic heteroaromatic ringhaving 1-5 heteroatoms independently selected from nitrogen, oxygen, orsulfur; L¹ is a C₁₋₂₀ bivalent, trivalent, or tetravalent straight orbranched hydrocarbon chain wherein 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10methylene units of the chain are independently and optionally replacedwith a natural or non-natural amino acid, —O—, —C(O)—, —C(O)O—, —OC(O)—,—N(R)—, —C(O)N(R)—, —(R)NC(O)—, —OC(O)N(R)—, —(R)NC(O)O—,—N(R)C(O)N(R)—, —S—, —SO—, —SO₂—, —SO₂N(R)—, —(R)NSO₂—, —C(S)—, —C(S)O—,—OC(S)—, —C(S)N(R)—, —(R)NC(S)—, —(R)NC(S)N(R)—, or -Cy-; and 1-20 ofthe methylene units of the chain are independently and optionallyreplaced with —OCH₂CH₂—; each -Cy- is independently a bivalentoptionally substituted 3-8 membered saturated or partially unsaturatedmonocyclic carbocyclic ring, optionally substituted phenylene, anoptionally substituted 4-8 membered saturated or partially unsaturatedmonocyclic heterocyclic ring having 1-3 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur, an optionally substituted 5-6membered monocyclic heteroaromatic ring having 1-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur, an optionallysubstituted 8-10 membered bicyclic or bridged bicyclic saturated orpartially unsaturated heterocyclic ring having 1-5 heteroatomsindependently selected from nitrogen, oxygen, or sulfur, or anoptionally substituted 8-10 membered bicyclic or bridged bicyclicheteroaromatic ring having 1-5 heteroatoms independently selected fromnitrogen, oxygen, or sulfur; and n is 0 or
 1. 15. A compound of FormulaX-b:

or a tautomer or pharmaceutically acceptable salt thereof, wherein: Ar¹is an optionally substituted phenyl or optionally substituted 5-6membered monocyclic heteroaromatic ring having 1-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; Ar² is anoptionally substituted 5-6 membered monocyclic heteroaromatic ringhaving 1-4 heteroatoms independently selected from nitrogen, oxygen, orsulfur, or an optionally substituted 8-10 membered bicyclicheteroaromatic ring having 1-5 heteroatoms independently selected fromnitrogen, oxygen, or sulfur; wherein one of Ar¹ or Ar² is substitutedwith one R²; X is selected from a bivalent C₁₋₃ alkylene chain wherein1-2 methylene units of the chain are independently and optionallyreplaced with —O—, —NR⁶—, —S—, —C(O)—, —CO₂——CS—, —C(NR⁶)—, —S(O)—, or—S(O)₂—; R¹ is selected from —C(O)R⁶, —CO₂R, —C(O)NR₂, —C₁₋₆ aliphatic,—CN, —(CH₂)₁₋₃OR, —(CH₂)₁₋₃NHR, —N(R)C(O)OR⁶, —N(R⁶)C(O)R, —OC(O)R, —OR,—NHR⁶, or —N(R)C(O)NHR; R² is a photoactivatable group that optionallycomprises a click-ready group if R³ is absent; R³ is absent or is aclick-ready group or a pull-down group; each R⁶ is independentlyhydrogen or C₁₋₆ alkyl optionally substituted with 1, 2, 3, 4, 5, or 6deuterium or halogen atoms; each R is independently hydrogen or anoptionally substituted group selected from C₁₋₆ aliphatic, a 3-8membered saturated or partially unsaturated monocyclic carbocyclic ring,phenyl, an 8-10 membered bicyclic aromatic carbocyclic ring, a 4-8membered saturated or partially unsaturated monocyclic heterocyclic ringhaving 1-2 heteroatoms independently selected from nitrogen, oxygen, orsulfur, a 5-6 membered monocyclic heteroaromatic ring having 1-4heteroatoms independently selected from nitrogen, oxygen, or sulfur, oran 8-10 membered bicyclic heteroaromatic ring having 1-5 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; L¹ is a C₁₋₂₀bivalent or trivalent straight or branched hydrocarbon chain wherein 1,2, 3, 4, 5, 6, 7, 8, 9, or 10 methylene units of the chain areindependently and optionally replaced with a natural or non-naturalamino acid, —O—, —C(O)—, —C(O)O—, —OC(O)—, —N(R)—, —C(O)N(R)—,—(R)NC(O)—, —OC(O)N(R)—, —(R)NC(O)O—, —N(R)C(O)N(R)—, —S—, —SO—, —SO₂—,—SO₂N(R)—, —(R)NSO₂—, —C(S)—, —C(S)O—, —OC(S)—, —C(S)N(R)—, —(R)NC(S)—,—(R)NC(S)N(R)—, or -Cy-; and 1-20 of the methylene units of the chainare independently and optionally replaced with —OCH₂CH₂—; each -Cy- isindependently a bivalent optionally substituted 3-8 membered saturatedor partially unsaturated monocyclic carbocyclic ring, optionallysubstituted phenylene, an optionally substituted 4-8 membered saturatedor partially unsaturated monocyclic heterocyclic ring having 1-3heteroatoms independently selected from nitrogen, oxygen, or sulfur, anoptionally substituted 5-6 membered monocyclic heteroaromatic ringhaving 1-4 heteroatoms independently selected from nitrogen, oxygen, orsulfur, an optionally substituted 8-10 membered bicyclic or bridgedbicyclic saturated or partially unsaturated heterocyclic ring having 1-5heteroatoms independently selected from nitrogen, oxygen, or sulfur, oran optionally substituted 8-10 membered bicyclic or bridged bicyclicheteroaromatic ring having 1-5 heteroatoms independently selected fromnitrogen, oxygen, or sulfur; and n is 0 or
 1. 16. (canceled)
 17. Thecompound of claim 14, wherein R² is selected from

wherein Y⁻ is a pharmaceutically acceptable anion.
 18. The compound ofclaim 14, wherein R³ is an azide, an alkyne, 4-dibenzocyclooctynol(DIBO) a gem-difluorinated cyclooctyne (DIFO or DFO),biarylazacyclooctynone (BARAC), bicyclononyne (BCN), a strainedcyclooctyne, an oxime, oxanorbornadiene, or biotin. 1-21. (canceled) 22.The compound of claim 14, wherein the compound is of Formulae XVI, XVII,XVIII, or XIX:

or a tautomer or pharmaceutically acceptable salt thereof. 23.(canceled)
 24. A compound of Formula XXV:

or a pharmaceutically acceptable salt thereof, wherein: Ar¹ is anoptionally substituted phenyl or optionally substituted 5-6 memberedmonocyclic heteroaromatic ring having 1-4 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur; Ar³ is an optionallysubstituted phenyl, an optionally substituted 5-6 membered monocyclicheteroaromatic ring having 1-4 heteroatoms independently selected fromnitrogen, oxygen, or sulfur, an optionally substituted 8-12 memberedbicyclic aromatic ring, or an optionally substituted 8-10 memberedbicyclic heteroaromatic ring having 1-5 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur; X is selected from a bivalentC₁₋₃ alkylene chain wherein 1-2 methylene units of the chain areindependently and optionally replaced with —O—, —NR⁶—, —S—, —C(O)—,—CO₂——CS—, —C(NR⁶)—, —S(O)—, or —S(O)₂—; X² is selected from a bivalentC₁₋₃ alkylene chain wherein 1-2 methylene units of the chain areindependently and optionally replaced with —O—, —NR⁶—, —S—, —C(O)—,—CO₂——CS—, —C(NR⁶)—, —S(O)—, or —S(O)₂—; R² is a photoactivatable groupthat optionally comprises a click-ready group if R³ is absent; R³ isabsent or is a click-ready group or a pull-down group; each R⁴ isindependently R, halogen, —CN, —NO₂, —OR, —SR, —NR₂, —S(O)₂R, —S(O)₂NR₂,—S(O)R, —C(O)R, —C(O)OR, —C(O)NR₂, —C(O)N(R)OR, —OC(O)R, —OC(O)NR₂,—N(R)C(O)OR, —N(R)C(O)R, —N(R)C(O)NR₂, —N(R)S(O)₂R, or —N(R)S(O)₂NR₂; ortwo instances of R⁴ may be taken together with the atoms to which theyare attached to form a C₄₋₈ partially unsaturated carbocyclic ring; eachR⁵ is independently R, halogen, —CN, —NO₂, —OR, —SR, —NR₂, —S(O)₂R,—S(O)₂NR₂, —S(O)R, —C(O)R, —C(O)OR, —C(O)NR₂, —C(O)N(R)OR, —OC(O)R,—OC(O)NR₂, —N(R)C(O)OR, —N(R)C(O)R, —N(R)C(O)NR₂, —N(R)S(O)₂R, or—N(R)S(O)₂NR₂; or two instances of R⁵ may be taken together to form ═Oor ═S; each R⁶ is independently hydrogen or C₁₋₆ alkyl optionallysubstituted with 1, 2, 3, 4, 5, or 6 deuterium or halogen atoms; each Ris independently hydrogen or an optionally substituted group selectedfrom C₁₋₆ aliphatic, a 3-8 membered saturated or partially unsaturatedmonocyclic carbocyclic ring, phenyl, an 8-10 membered bicyclic aromaticcarbocyclic ring, a 4-8 membered saturated or partially unsaturatedmonocyclic heterocyclic ring having 1-2 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur, a 5-6 membered monocyclicheteroaromatic ring having 1-4 heteroatoms independently selected fromnitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaromaticring having 1-5 heteroatoms independently selected from nitrogen,oxygen, or sulfur; L² is a C₁₋₂₀ bivalent or trivalent, straight orbranched, optionally substituted hydrocarbon chain wherein 1, 2, 3, 4,5, 6, 7, 8, 9, or 10 methylene units of the chain are independently andoptionally replaced with a natural or non-natural amino acid, —O—,—C(O)—, —C(O)O—, —OC(O)—, —N(R)—, —C(O)N(R)—, —(R)NC(O)—, —OC(O)N(R)—,—(R)NC(O)O—, —N(R)C(O)N(R)—, —S—, —SO—, —SO₂—, —SO₂N(R)—, —(R)NSO₂—,—C(S)—, —C(S)O—, —OC(S)—, —C(S)N(R)—, —(R)NC(S)—, —(R)NC(S)N(R)—, or-Cy-; and 1-20 of the methylene units of the chain are independently andoptionally replaced with —OCH₂CH₂—; each -Cy- is independently abivalent optionally substituted 3-8 membered saturated or partiallyunsaturated monocyclic carbocyclic ring, optionally substitutedphenylene, an optionally substituted 4-8 membered saturated or partiallyunsaturated monocyclic heterocyclic ring having 1-3 heteroatomsindependently selected from nitrogen, oxygen, or sulfur, an optionallysubstituted 5-6 membered monocyclic heteroaromatic ring having 1-4heteroatoms independently selected from nitrogen, oxygen, or sulfur, anoptionally substituted 8-10 membered bicyclic or bridged bicyclicsaturated or partially unsaturated heterocyclic ring having 1-5heteroatoms independently selected from nitrogen, oxygen, or sulfur, oran optionally substituted 8-10 membered bicyclic or bridged bicyclicheteroaromatic ring having 1-5 heteroatoms independently selected fromnitrogen, oxygen, or sulfur; m is 0, 1, 2, 3, or 4; and p is 0, 1, 2, 3,or
 4. 25. A compound of Formula XXVI:

or a pharmaceutically acceptable salt thereof, wherein: Ar¹ is anoptionally substituted phenyl or optionally substituted 5-6 memberedmonocyclic heteroaromatic ring having 1-4 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur; Ar³ is an optionallysubstituted phenyl, an optionally substituted 5-6 membered monocyclicheteroaromatic ring having 1-4 heteroatoms independently selected fromnitrogen, oxygen, or sulfur, an optionally substituted 8-12 memberedbicyclic aromatic ring, or an optionally substituted 8-10 memberedbicyclic heteroaromatic ring having 1-5 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur; X is selected from a bivalentC₁₋₃ alkylene chain wherein 1-2 methylene units of the chain areindependently and optionally replaced with —O—, —NR⁶—, —S—, —C(O)—,—CO₂——CS—, —C(NR⁶)—, —S(O)—, or —S(O)₂—; X² is selected from a bivalentC₁₋₃ alkylene chain wherein 1-2 methylene units of the chain areindependently and optionally replaced with —O—, —NR⁶—, —S—, —C(O)—,—CO₂——CS—, —C(NR⁶)—, —S(O)—, or —S(O)₂—; R² is a photoactivatable groupthat optionally comprises a click-ready group if R³ is absent; R³ isabsent or is a click-ready group or a pull-down group; each R⁴ isindependently R, halogen, —CN, —NO₂, —OR, —SR, —NR₂, —S(O)₂R, —S(O)₂NR₂,—S(O)R, —C(O)R, —C(O)OR, —C(O)NR₂, —C(O)N(R)OR, —OC(O)R, —OC(O)NR₂,—N(R)C(O)OR, —N(R)C(O)R, —N(R)C(O)NR₂, —N(R)S(O)₂R, or —N(R)S(O)₂NR₂; ortwo instances of R⁴ may be taken together with the atoms to which theyare attached to form a C₄₋₈ partially unsaturated carbocyclic ring; eachR⁵ is independently R, halogen, —CN, —NO₂, —OR, —SR, —NR₂, —S(O)₂R,—S(O)₂NR₂, —S(O)R, —C(O)R, —C(O)OR, —C(O)NR₂, —C(O)N(R)OR, —OC(O)R,—OC(O)NR₂, —N(R)C(O)OR, —N(R)C(O)R, —N(R)C(O)NR₂, —N(R)S(O)₂R, or—N(R)S(O)₂NR₂; or two instances of R⁵ may be taken together to form ═Oor ═S; each R⁶ is independently hydrogen or C₁₋₆ alkyl optionallysubstituted with 1, 2, 3, 4, 5, or 6 deuterium or halogen atoms; each R⁷is independently R, halogen, —CN, —NO₂, —OR, —SR, —NR₂, —S(O)₂R,—S(O)₂NR₂, —S(O)R, —C(O)R, —C(O)OR, —C(O)NR₂, —C(O)N(R)OR, —OC(O)R,—OC(O)NR₂, —N(R)C(O)OR, —N(R)C(O)R, —N(R)C(O)NR₂, —N(R)S(O)₂R, or—N(R)S(O)₂NR₂; or two instances of R⁴ may be taken together with theatoms to which they are attached to form a C₄₋₈ partially unsaturatedcarbocyclic ring; each R is independently hydrogen or an optionallysubstituted group selected from C₁₋₆ aliphatic, a 3-8 membered saturatedor partially unsaturated monocyclic carbocyclic ring, phenyl, an 8-10membered bicyclic aromatic carbocyclic ring, a 4-8 membered saturated orpartially unsaturated monocyclic heterocyclic ring having 1-2heteroatoms independently selected from nitrogen, oxygen, or sulfur, a5-6 membered monocyclic heteroaromatic ring having 1-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur, or an 8-10membered bicyclic heteroaromatic ring having 1-5 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; L² is a C₁₋₂₀bivalent or trivalent, straight or branched, optionally substitutedhydrocarbon chain wherein 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 methyleneunits of the chain are independently and optionally replaced with anatural or non-natural amino acid, —O—, —C(O)—, —C(O)O—, —OC(O)—,—N(R)—, —C(O)N(R)—, —(R)NC(O)—, —OC(O)N(R)—, —(R)NC(O)O—,—N(R)C(O)N(R)—, —S—, —SO—, —SO₂—, —SO₂N(R)—, —(R)NSO₂—, —C(S)—, —C(S)O—,—OC(S)—, —C(S)N(R)—, —(R)NC(S)—, —(R)NC(S)N(R)—, or -Cy-; and 1-20 ofthe methylene units of the chain are independently and optionallyreplaced with —OCH₂CH₂—; each -Cy- is independently a bivalentoptionally substituted 3-8 membered saturated or partially unsaturatedmonocyclic carbocyclic ring, optionally substituted phenylene, anoptionally substituted 4-8 membered saturated or partially unsaturatedmonocyclic heterocyclic ring having 1-3 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur, an optionally substituted 5-6membered monocyclic heteroaromatic ring having 1-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur, an optionallysubstituted 8-10 membered bicyclic or bridged bicyclic saturated orpartially unsaturated heterocyclic ring having 1-5 heteroatomsindependently selected from nitrogen, oxygen, or sulfur, or anoptionally substituted 8-10 membered bicyclic or bridged bicyclicheteroaromatic ring having 1-5 heteroatoms independently selected fromnitrogen, oxygen, or sulfur; m is 0, 1, 2, 3, or 4; and p is 0, 1, 2, 3,or
 4. 26-34. (canceled)
 35. The compound of claim 24, wherein thecompound is of Formulae XXIX, XXX, XXXI, XXXII, or XXXIII:

or a pharmaceutically acceptable salt thereof.
 36. The compound of claim25, wherein the compound is of Formulae XXXVIII, XXXIX, XL, XLI, orXLII:

or a pharmaceutically acceptable salt thereof.
 37. (canceled)
 38. An RNAconjugate, comprising a target RNA and a compound of claim 1, whereinR^(mod) forms a covalent bond to the target RNA.
 39. A method ofdetermining the three-dimensional structure, binding site of a ligand ofinterest, or accessibility of a nucleotide in a target nucleic acid,comprising: contacting the target nucleic acid with a compound of claim1 or a pharmaceutically acceptable salt thereof; irradiating thecompound; determining whether covalent modification of a nucleotide ofthe nucleic acid has occurred; and optionally deriving the pattern ofnucleotide modification, the three-dimensional structure, ligand bindingsite, or other structural information about the nucleic acid.
 40. Amethod of preparing a nucleic acid conjugate, comprising: contacting atarget nucleic acid with a compound of claim 1 or a pharmaceuticallyacceptable salt thereof; irradiating the compound; and optionallyisolating the resulting nucleic acid conjugate by an affinity assay, orother pull-down method.
 41. A method of preparing an RNA conjugate,comprising: contacting a target RNA with a compound of claim 1 or apharmaceutically acceptable salt thereof; irradiating the compound; andoptionally isolating the resulting RNA conjugate by an affinity assay orpull-down method.
 42. A method of assessing selectivity across atranscriptome for a drug candidate, comprising: contacting a biologicalsample comprising two or more RNA transcripts with a compound of claim 1or a pharmaceutically acceptable salt thereof; irradiating thebiological sample; and determining a site of covalent modification ofthe two or more RNA transcripts.
 43. A method of determining targetoccupancy of a drug candidate in cells, comprising: contacting abiological sample with a compound of claim 1 or a pharmaceuticallyacceptable salt thereof, wherein the biological sample comprises cellsthat comprise a target RNA; irradiating the biological sample; anddetermining a site of covalent modification of the target RNA.